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Offline blackngold29

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Google Interview Questions
« on: September 13, 2011, 08:27:22 PM »
I thought this might make some interesting discussion, the following are questions asked when they interview you at Google. Answer one or all them:

https://www.businessinsider.com/15-google-interview-questions-that-will-make-you-feel-stupid-2009-11#

How many golf balls can fit in a school bus?

How much should you charge to wash all the windows in Seattle?

In a country in which people only want boys every family continues to have children until they have a boy. If they have a girl, they have another child. If they have a boy, they stop. What is the proportion of boys to girls in the country?

How many piano tuners are there in the entire world?

Why are manhole covers round?

Design an evacuation plan for San Francisco.

How many times a day does a clock’s hands overlap?

Explain the significance of "dead beef"

A man pushed his car to a hotel and lost his fortune. What happened?

You need to check that your friend, Bob, has your correct phone number, but you cannot ask him directly. You must write the question on a card which and give it to Eve who will take the card to Bob and return the answer to you. What must you write on the card, besides the question, to ensure Bob can encode the message so that Eve cannot read your phone number?

You're the captain of a pirate ship and your crew gets to vote on how the gold is divided up. If fewer than half of the pirates agree with you, you die. How do you recommend apportioning the gold in such a way that you get a good share of the booty, but still survive?

You have eight balls all of the same size 7 of them weigh the same, and one of them weighs slightly more. How can you find the ball that is heavier by using a balance and only two weighings?

You are given 2 eggs. You have access to a 100-story building. Eggs can be very hard or very fragile means it may break if dropped from the first floor or may not even break if dropped from 100th floor. Both eggs are identical. You need to figure out the highest floor of a 100-story building an egg can be dropped without breaking. The question is how many drops you need to make. You are allowed to break 2 eggs in the process.

Explain a database in three sentences to your eight-year-old nephew.

You are shrunk to the height of a nickel and your mass is proportionally reduced so as to maintain your original density. You are then thrown into an empty glass blender. The blades will start moving in 60 seconds. What do you do?

Offline Implode

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Re: Google Interview Questions
« Reply #1 on: September 13, 2011, 09:19:00 PM »
I've seen this list before. Pretty cool.

You need to check that your friend, Bob, has your correct phone number, but you cannot ask him directly. You must write the question on a card which and give it to Eve who will take the card to Bob and return the answer to you. What must you write on the card, besides the question, to ensure Bob can encode the message so that Eve cannot read your phone number?

"Call me."

You have eight balls all of the same size 7 of them weigh the same, and one of them weighs slightly more. How can you find the ball that is heavier by using a balance and only two weighings?

Assuming that you're using a balance, weigh two groups of three. If they are the same, weigh the remaining two to find the heavier ball. If one set of three is heavier, then weigh two balls from that group to find the heavier one. If they are equal, the remaining ball is heavier.

Offline axeman90210

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Re: Google Interview Questions
« Reply #2 on: September 13, 2011, 09:26:25 PM »

You're the captain of a pirate ship and your crew gets to vote on how the gold is divided up. If fewer than half of the pirates agree with you, you die. How do you recommend apportioning the gold in such a way that you get a good share of the booty, but still survive?


If your crew has x number of pirates and a chest of gold worth  y, they can reasonably expect to get y/x of the gold in a fair split. If you offer half of your crew (y/x)+.01 worth of the gold, they will vote yes because they now get a better share than they otherwise would have expected, you then get to pocket everything that's left
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Offline Chino

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Re: Google Interview Questions
« Reply #3 on: September 13, 2011, 09:48:41 PM »

How many golf balls can fit in a school bus?

-(Volume of the bus - the seat space) / the dimension of a golf ball

How much should you charge to wash all the windows in Seattle?

- find out the area of all windows in seatle, then hold an auction amongst mexicans for the lowest bidder. Gonfrom there.

In a country in which people only want boys every family continues to have children until they have a boy. If they have a girl, they have another child. If they have a boy, they stop. What is the proportion of boys to girls in the country?

- Boys:Girls

How many piano tuners are there in the entire world?

- piano tuners < than the number of pianos

Why are manhole covers round?

- structural integrity

Design an evacuation plan for San Francisco.

- tell everyone to head east while I book for the pacific and avoid crowds.

How many times a day does a clock’s hands overlap?

- 24 hours if analog, zero if digital.

Explain the significance of "dead beef"

- it fills the void when bacon is not present

A man pushed his car to a hotel and lost his fortune. What happened?

- he ran out of gas after leaving the Chinese buffet. He left his fortune on the table by mistake.

You need to check that your friend, Bob, has your correct phone number, but you cannot ask him directly. You must write the question on a card which and give it to Eve who will take the card to Bob and return the answer to you. What must you write on the card, besides the question, to ensure Bob can encode the message so that Eve cannot read your phone number?

- bob, can you please call me ASAP?

You're the captain of a pirate ship and your crew gets to vote on how the gold is divided up. If fewer than half of the pirates agree with you, you die. How do you recommend apportioning the gold in such a way that you get a good share of the booty, but still survive?

- don't take any initially. Let everyone vote until only you and one other pirate are left.

You have eight balls all of the same size 7 of them weigh the same, and one of them weighs slightly more. How can you find the ball that is heavier by using a balance and only two weighings?

- weigh 6 initially. If they are balanced, then you can determine which of the two remaining is lighter. If one of the original sets of three is lighter, just weigh two balls from the lighter batch and you'll find it.

You are given 2 eggs. You have access to a 100-story building. Eggs can be very hard or very fragile means it may break if dropped from the first floor or may not even break if dropped from 100th floor. Both eggs are identical. You need to figure out the highest floor of a 100-story building an egg can be dropped without breaking. The question is how many drops you need to make. You are allowed to break 2 eggs in the process.

You only need one drop. Drop it from the top floor. Make a parachute for it out of a garbage bag.

Explain a database in three sentences to your eight-year-old nephew.

- an information bank

You are shrunk to the height of a nickel and your mass is proportionally reduced so as to maintain your original density. You are then thrown into an empty glass blender. The blades will start moving in 60 seconds. What do you do?

If you are skinny lay down, or grab onto a blade and hold on. Try to get near the centernof the blade to prevent motion sickness.
« Last Edit: September 14, 2011, 05:27:40 AM by Chino »

Offline rumborak

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Re: Google Interview Questions
« Reply #4 on: September 14, 2011, 11:36:05 AM »
Whoa, many wrong or misunderstood answers here. My take on some of them:

How many golf balls can fit in a school bus?

~5cm diameter of a golf ball. ~6 meters x 2 meters x 3 meters of the school bus. Assuming the simplest egg-crate packing of the balls, it's 35m^3/0.000125m^3 = 280,000. Add another 15% for the more realistic and more efficient packing of the balls, and you got ~320,000 balls.

Quote
How much should you charge to wash all the windows in Seattle?

Get the revenue sales for Windex for Seattle, find out how many windows you can wash with a bottle of Windex, that gives you the number of windows. find out how many windows you can wash per hour, set your desired hourly salary, there you go.

Quote
In a country in which people only want boys every family continues to have children until they have a boy. If they have a girl, they have another child. If they have a boy, they stop. What is the proportion of boys to girls in the country?

The probability of boy vs. girl is 0.5. So, probability of boy first time = 0.5. Probability of boy second time around, 0.5*0.5 = 0.25. Etc.
From that probability distribution you can get a formula for the expected value of girls and boys. Take the ratio, do the limit to infinity, there you go.

Quote
Why are manhole covers round?

They are round because there is no way of turning them so that they would fall in.

Quote
Explain a database in three sentences to your eight-year-old nephew.

It's a big shoebox that keeps everything you put in, and you always know where to find the thing you're looking for.

Quote
You are shrunk to the height of a nickel and your mass is proportionally reduced so as to maintain your original density. You are then thrown into an empty glass blender. The blades will start moving in 60 seconds. What do you do?

Stand in the center, ride the cyclone up.

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Offline rumborak

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Re: Google Interview Questions
« Reply #5 on: September 14, 2011, 11:41:48 AM »
- an information bank

8-year old have little concept of what either "information" is, or what a bank really does (other than mom and pop going there to get money).

rumborak
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Offline Dr. DTVT

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Re: Google Interview Questions
« Reply #6 on: September 14, 2011, 11:57:14 AM »
Most of them are easy if you think about them.  Just to take the egg one, it will take (N/2)+1 drops to figure out what floor it can survive from, where N is the floor it will .  You have two eggs, so you drop for the second floor.  If it survives, go up to floors, if it doesn't go down a floor and test.
     

Offline rumborak

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Re: Google Interview Questions
« Reply #7 on: September 14, 2011, 12:05:24 PM »
You can do better than that though. Drop the first egg from the 50th floor. If it breaks you have to do the (worst-case) 49 floors from the first up to see where the second egg breaks. If the first doesn't break, you can then drop it from the 75th floor, thereby once again cutting the search space in half. And so on.

rumborak
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Offline Dr. DTVT

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Re: Google Interview Questions
« Reply #8 on: September 14, 2011, 12:28:39 PM »
Do the math.  Your method produces 50 drops if it's the 49th floor.  Mine takes 26.  My method always produces a minimum number.
     

Offline Ravenheart

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Re: Google Interview Questions
« Reply #9 on: September 14, 2011, 12:30:27 PM »
These sorts of questions always make me feel really stupid.

Offline alirocker08

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Re: Google Interview Questions
« Reply #10 on: September 14, 2011, 12:31:01 PM »
How many golf balls can fit in a school bus?
Why would you want to put Golf Balls into a school bus? Surely the primary purpose of a school bus is to transport children to school, not golf balls. Unless it's golf ball school, then you would have to adjust the size of the bus so that each individual golf ball has its own seat to prevent overcrowding. Could be dangerous if the bus hit a bump in the road, golf balls bumping into one another could cause them to get damaged. And if these golf balls are entitled to an education, they should be liable to sue you as well.

How much should you charge to wash all the windows in Seattle?
Window washing isn't the area of work I want to go into. This question is completely irrelevant to me.

In a country in which people only want boys every family continues to have children until they have a boy. If they have a girl, they have another child. If they have a boy, they stop. What is the proportion of boys to girls in the country?

I'm not sure about this one, but I'm assuming this might mean a lot of lonely girls </3

How many piano tuners are there in the entire world?
Not enough, I could do with one to tune my piano downstairs, it hasn't been tuned in forever.

Why are manhole covers round?
It's like sorting shapes, but with fat people. Will the fat person fit through the square man hole? Noooooo, will the fat person fit through the circle manhole? Yesssss!

Design an evacuation plan for San Francisco.
Shit bricks.

How many times a day does a clock’s hands overlap?
Technically all the time. The clocks hands overlap at the centre of the clock.

Explain the significance of "dead beef"
When you have 'beef' with someone, you tend to have something against them. 'Dead beef' is where you put that grudge aside and make good friends with the person who you had the beef with.

A man pushed his car to a hotel and lost his fortune. What happened?
He had a drunken wager with one of his friends that he couldn't push his car all the way to the hotel, and bet his whole fortune. His friend twisted the man's words around when they made the wager, so the man believe that he would lose his fortune if he didn't push his car all the way to the hotel. In a drunken stupor, he began the arduous journey towards the hotel, car in front of him. Many turned out to see this feat of drunken strength, and he soon had a cult following cheering him on. Invigorated but near collapse, he carried on until he got to the hotel parking lot. His friend drove up to him, made him sign over his fortune, and he was left penniless asides from his car. To add insult to injury, in a rage he pushed the car into the hotel, and was fined for vandalism.

You need to check that your friend, Bob, has your correct phone number, but you cannot ask him directly. You must write the question on a card which and give it to Eve who will take the card to Bob and return the answer to you. What must you write on the card, besides the question, to ensure Bob can encode the message so that Eve cannot read your phone number?
'Facebook?', or seeing as this is for a Google interview, 'Google+'. Who uses phones now anyways?

You're the captain of a pirate ship and your crew gets to vote on how the gold is divided up. If fewer than half of the pirates agree with you, you die. How do you recommend apportioning the gold in such a way that you get a good share of the booty, but still survive?

Women were said to be bad luck on pirate ships, I wouldn't have this issue as they wouldn't let me on board, never mind become the captain.

You have eight balls all of the same size 7 of them weigh the same, and one of them weighs slightly more. How can you find the ball that is heavier by using a balance and only two weighings?
You wouldn't need the balance, simply picking them up two at a time should give you enough indication of which one is the heavier one, even if there is a slight difference. It's kind of like an eye test, in an eye test there is some inkling which lense is clearer, even if there is only a slight difference.

You are given 2 eggs. You have access to a 100-story building. Eggs can be very hard or very fragile means it may break if dropped from the first floor or may not even break if dropped from 100th floor. Both eggs are identical. You need to figure out the highest floor of a 100-story building an egg can be dropped without breaking. The question is how many drops you need to make. You are allowed to break 2 eggs in the process.
I would refuse to participate in this experiment, as even though these two eggs are identical in fragility, other eggs can be harder or more fragile, therefore rendering this experiment useless as it doesn't apply to all eggs. Not only that, but there would almost certainly be people walking around underneath your 100 story building, and I wouldn't want to risk egging someone and having to pay them to have their suits dry cleaned or whatever.

Explain a database in three sentences to your eight-year-old nephew.
Google it. Seriously kid. Google it.

You are shrunk to the height of a nickel and your mass is proportionally reduced so as to maintain your original density. You are then thrown into an empty glass blender. The blades will start moving in 60 seconds. What do you do?
Marvel at the fact that I've been made smaller than I am already. The sheer wonder at this magnificent feat would distract me from the blender blades, thus making my death relatively painless as I wouldn't see it coming, and I wouldn't be tensed up in fear.

I expect the job offers from Google to come flooding in.
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Offline Dimitrius

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Re: Google Interview Questions
« Reply #11 on: September 14, 2011, 03:29:35 PM »
A man pushed his car to a hotel and lost his fortune. What happened?
He's playing Monopoly.
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Offline 7StringedBeast

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Re: Google Interview Questions
« Reply #12 on: September 14, 2011, 04:03:33 PM »
A man pushed his car to a hotel and lost his fortune. What happened?
He's playing Monopoly.

Brilliant!
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Offline Implode

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Re: Google Interview Questions
« Reply #13 on: September 14, 2011, 05:59:25 PM »
A man pushed his car to a hotel and lost his fortune. What happened?
He's playing Monopoly.
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Re: Google Interview Questions
« Reply #14 on: September 14, 2011, 06:25:59 PM »
A man pushed his car to a hotel and lost his fortune. What happened?
He's playing Monopoly.
You're hired.

Offline blackngold29

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Re: Google Interview Questions
« Reply #15 on: September 14, 2011, 09:04:54 PM »
For the window washing one I would say, "$X per window."

Most of them I would probably be fucked. Though I strongly suspect this would be one of those 'how you answer, not what you say' kind of activities. Then again, most Googlers are probably better at math than me.

Offline MetalManiac666

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Re: Google Interview Questions
« Reply #16 on: September 14, 2011, 09:42:28 PM »

Offline Chino

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Re: Google Interview Questions
« Reply #17 on: September 14, 2011, 11:02:55 PM »
For the window washing one I would say, "$X per window."

Most of them I would probably be fucked. Though I strongly suspect this would be one of those 'how you answer, not what you say' kind of activities. Then again, most Googlers are probably better at math than me.

Google is all about outside the box thinking. They don't want real answers, they want to see imagination.

Offline rumborak

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Re: Google Interview Questions
« Reply #18 on: September 14, 2011, 11:25:09 PM »
Do the math.  Your method produces 50 drops if it's the 49th floor.  Mine takes 26.  My method always produces a minimum number.

If the egg breaks at the 100th floor, your method takes 50 steps. So no, it's not really better.

The real solution is more elaborate, but expands on my "binary search" algorithm, only that it optimizes the remaining linear search for the second egg:

https://classic-puzzles.blogspot.com/2006/12/google-interview-puzzle-2-egg-problem.html

rumborak
« Last Edit: September 14, 2011, 11:30:28 PM by rumborak »
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Offline ReaPsTA

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Re: Google Interview Questions
« Reply #19 on: September 14, 2011, 11:52:47 PM »
I'm retarded with these problems.  I feel it creates a huge gap in my thinking.
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Offline Perpetual Change

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Re: Google Interview Questions
« Reply #20 on: September 15, 2011, 06:58:29 AM »
I don't really get the point of these questions.

Offline XJDenton

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Re: Google Interview Questions
« Reply #21 on: September 15, 2011, 07:17:05 AM »
I don't really get the point of these questions.

Problem solving. Its to demonstrate how you approach problems when you don't necessarily have quantitative information.
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Offline Perpetual Change

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Re: Google Interview Questions
« Reply #22 on: September 15, 2011, 07:20:32 AM »
Well, considering I would probably not be able to solve any of those problems with quantitative information, I suddenly feel like a dumbass.

Offline Chino

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Re: Google Interview Questions
« Reply #23 on: September 15, 2011, 08:36:57 AM »
Well, considering I would probably not be able to solve any of those problems with quantitative information, I suddenly feel like a dumbass.

Don't think of yourself as a dumbass, you're just not worthy by google standards.

Offline Perpetual Change

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Re: Google Interview Questions
« Reply #24 on: September 15, 2011, 08:38:34 AM »
Not as worthy as Google Wave, Buzz, and Plus, right?

:neverusethis:

Offline jasc15

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Re: Google Interview Questions
« Reply #25 on: September 15, 2011, 11:39:29 AM »
I posted a thread asking question #7 a while back, except I asked when the hands would be at 90 degrees (same thing).  I think the answer was 22 times on a 12 hour clock.

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Re: Google Interview Questions
« Reply #26 on: September 15, 2011, 01:35:27 PM »
Do the math.  Your method produces 50 drops if it's the 49th floor.  Mine takes 26.  My method always produces a minimum number.

If the egg breaks at the 100th floor, your method takes 50 steps. So no, it's not really better.

The real solution is more elaborate, but expands on my "binary search" algorithm, only that it optimizes the remaining linear search for the second egg:

https://classic-puzzles.blogspot.com/2006/12/google-interview-puzzle-2-egg-problem.html

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Offline Chino

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Re: Google Interview Questions
« Reply #27 on: September 15, 2011, 01:51:44 PM »
I posted a thread asking question #7 a while back, except I asked when the hands would be at 90 degrees (same thing).  I think the answer was 22 times on a 12 hour clock.

Technically both hands start at the same point (the middle). The minute hand sits directly above the hour hand. Doesn't that mean the the hands are overlapping at all times?

Offline jasc15

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Re: Google Interview Questions
« Reply #28 on: September 16, 2011, 06:45:20 AM »
I posted a thread asking question #7 a while back, except I asked when the hands would be at 90 degrees (same thing).  I think the answer was 22 times on a 12 hour clock.

Technically both hands start at the same point (the middle). The minute hand sits directly above the hour hand. Doesn't that mean the the hands are overlapping at all times?
When are the hands pointing in the exact same direction?  You can start at 12:00, then it will happen again at some time after 1:00.  The minute hand has to move a bit more than an hour each time around to reach the hour hand.

Offline Xanthul

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Re: Google Interview Questions
« Reply #29 on: September 16, 2011, 07:07:23 AM »
I posted a thread asking question #7 a while back, except I asked when the hands would be at 90 degrees (same thing).  I think the answer was 22 times on a 12 hour clock.

Technically both hands start at the same point (the middle). The minute hand sits directly above the hour hand. Doesn't that mean the the hands are overlapping at all times?
When are the hands pointing in the exact same direction?  You can start at 12:00, then it will happen again at some time after 1:00.  The minute hand has to move a bit more than an hour each time around to reach the hour hand.

I think he means that since the hands are rooted at the same spot (one above the other), technically they overlap all the time, which I think would be a valid answer.

About pointing in the exact same direction, I think the answer would be 24 times. All hours have their minute equivalents (1:05, 2:10, etc) so hands are bound to overlap completely once each hour (which makes sense, the minutes hand has to do a full circle every hour so it necessarily will pass the hour hand once). All these minutes that you "lose" from one hour to the next (they overlap every 1:05 instead of 1:00) you get back in the last hour (from 11:55 to 12:00, which is just 5 minutes).

Offline jasc15

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Re: Google Interview Questions
« Reply #30 on: September 16, 2011, 11:28:35 AM »
I think he means that since the hands are rooted at the same spot (one above the other), technically they overlap all the time, which I think would be a valid answer.
Well, if that's the case, then I guess I fail at out of the box thinking (no surpise to me)

Quote
About pointing in the exact same direction, I think the answer would be 24 times. All hours have their minute equivalents (1:05, 2:10, etc) so hands are bound to overlap completely once each hour (which makes sense, the minutes hand has to do a full circle every hour so it necessarily will pass the hour hand once). All these minutes that you "lose" from one hour to the next (they overlap every 1:05 instead of 1:00) you get back in the last hour (from 11:55 to 12:00, which is just 5 minutes).
It wouldn't be exactly 1:05, since the hour hand moved slightly when the minute hand is at 5 minutes, but its good enough to figure out the number of occurrences.  Also, the occurrence just prior to 12:00pm would be 10:55am, not 11:55am, which is the 10th occurrence since 12:00am, which is 11 times in 12 hours.