Microsoft Brain Teaser
Work this brain teaser with your team. It suggested by one of my graduate students for fun.
Four people are standing on one side of a bridge. They must all attend a meeting on the other
side, and the meeting begins in 17 minutes. The bridge can only support two people at a time. It
is a dark night, and each party crossing the bridge--either one or two people--must carry a
flashlight. And there is only one flashlight! Each person walks at a different rate, and any pair
must walk together at the rate of the slower person. The flashlight cannot be thrown back across
the bridge, but must be carried all the way back after each crossing. Find the correct sequence
that enables the four people to cross the bridge so that all arrive in 17 minutes, given these
crossing times: Amanda (1 minute); Bobby (2 minutes); Thomas (5 minutes); Zack (10 minutes).
Evidently, Microsoft asks this question to prospective employees. To become a Microserf, you
must answer in 5 minutes. There are no tricks. There are two solutions. It is said that 50
Motorola engineers failed to solve the problem. One guy solved it by a computer program,
requiring 37 minutes to write. About half the students in my lab have solved it, but all required
more than 5 minutes. A visiting professor from Turkey solved it in 30 minutes. No one in our
group has written the computer program to solve it yet, let alone write it in just 37 minutes. A
Russian chemical engineer, who was formerly the top high school math student in all Russia,
solved it almost immediately. I guess he could be a Microserf, but ChE is just as profitable.
Have fun!
What has this problem got to do with polymer science, if anything?
Grading Criteria
A valid solution: 4 points
What has it got to do with polymer science? 6 points (error-free grammar,
spelling, concise argument, cyclical writing).