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These three riddles appeared during a certain Microsoft job interview.

The interviewer would watch how the interviewee responds to these riddles. Even if they didn't get the answer, the interviewer wants to see how they think as they explain the steps they're making to TRY to solve it. Some might be too easy to solve directly! See if you can solve these.

Riddle #1:

1

1 1

2 1

1 2 1 1

1 1 1 2 2 1

3 1 2 2 1 1

What's the pattern?

Riddle #2:

You have four people at a bridge... one HAS to carry a flashlight as they cross, but only two can cross at a time. And nobody can go alone.

It only takes one 1 minute to cross. Another takes 2 minutes. Another, 5. And the last, 10.

If the person who takes 1 minute goes with the person who takes 10... it automatically takes 10 minutes.

How many minutes will it take them all to cross.. at the quickest?

Riddle #3:

You have two fuses... they burn at different rates and not at steady rates. BUT! They only burn for one hour. One could burn the entire way except one inch within one minute, then spend the last 59 on that last inch, for example.

You also have to use this to somehow time 45 minutes exactly. How would you do it?

The interviewer would watch how the interviewee responds to these riddles. Even if they didn't get the answer, the interviewer wants to see how they think as they explain the steps they're making to TRY to solve it. Some might be too easy to solve directly! See if you can solve these.

Riddle #1:

1

1 1

2 1

1 2 1 1

1 1 1 2 2 1

3 1 2 2 1 1

What's the pattern?

Riddle #2:

You have four people at a bridge... one HAS to carry a flashlight as they cross, but only two can cross at a time. And nobody can go alone.

It only takes one 1 minute to cross. Another takes 2 minutes. Another, 5. And the last, 10.

If the person who takes 1 minute goes with the person who takes 10... it automatically takes 10 minutes.

How many minutes will it take them all to cross.. at the quickest?

Riddle #3:

You have two fuses... they burn at different rates and not at steady rates. BUT! They only burn for one hour. One could burn the entire way except one inch within one minute, then spend the last 59 on that last inch, for example.

You also have to use this to somehow time 45 minutes exactly. How would you do it?

Last edited by PHY on December 6th, 2006, 10:33 pm, edited 1 time in total.

- PHY
**Posts:**223**Joined:**June 22nd, 2006, 4:03 pm

#1

The next two lines should be

1 3 1 1 2 2 2 1

1 1 1 3 2 1 3 2 1 1

#2

Smallest time I get is 18 minutes. Have the quickest person accompany the slowest person from the set and return across the bridge. Are there any other constraints? This is similar to the chicken, cat, fox riddle.

#3

? Seems like there isn't enough info. Will think some more.

The next two lines should be

1 3 1 1 2 2 2 1

1 1 1 3 2 1 3 2 1 1

#2

Smallest time I get is 18 minutes. Have the quickest person accompany the slowest person from the set and return across the bridge. Are there any other constraints? This is similar to the chicken, cat, fox riddle.

#3

? Seems like there isn't enough info. Will think some more.

- BenTheMan
**Posts:**5**Joined:**August 11th, 2006, 10:07 pm**Location:**Columbus, OH

louis002 wrote:For the 3rd riddle you have to burn both ends of the fuse to obtain the 30-minute point, and then start with that point and burn both ends of the second fuse.

Hi,

Thanks very much for this comment. It help me to think about my ideals.

Tks again and pls keep posting.

- vegetablevn
**Posts:**1**Joined:**August 21st, 2010, 8:57 am

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