Math Is Fun Forum

http://www.timesonline.co.uk/tol/life_a … 526400.ece

Some example 'Microsoft questions' ... discuss your answers!

1. How would you weigh a jet plane without using scales?

2. Why are manhole covers round rather than square?

3. Why is it that, when you turn on the hot water in a hotel, the hot water comes out instantly?

4. How do they make M&Ms?

5. How many times a day do a clock’s hands overlap?

6. You have eight billiard balls. One of them is “defective”, meaning that it weighs more than the others. How do you tell, using a balance, which ball is defective in two weighings?

7. You have two jars and 100 marbles. Fifty of the marbles are red, and 50 are blue. One of the jars will be chosen at random; then one marble will be withdrawn from that jar at random. How do you maximise the chance that a red marble will be chosen? (You must place all 100 marbles in the jars.) What is the chance of selecting a red marble when using your scheme?

8. You have a three-quart bucket, a five-quart bucket, and an infinite supply of water. How can you measure out exactly four quarts?

9. You have a bucket of jelly beans in three colours — red, green, and blue. With your eyes closed, you have to reach in the bucket and take out two jelly beans of the same color. How many jelly beans do you have to take to be certain of getting two the same colour?

10. Four people must cross a rickety footbridge at night. Many planks are missing, and the bridge can hold only two people at a time (any more than two, and the bridge collapses). The travellers must use a flashlight to guide their steps; otherwise they’re sure to step through a missing space and fall to their death. There is only one flashlight. The four people each travel at different speeds. Adam can cross the bridge in one minute; Larry in two minutes; Edge takes five minutes; and the slowest person, Bono, needs ten minutes. The bridge is going to collapse in exactly 17 minutes. How can all four people cross the bridge?

11. Why are beer cans tapered at the top and bottom?

12. How long would it take to move Mount Fuji?