Saturday, October 11, 2008

Riddles

Here are two from a good friend of mine, from Seattle:

#1
You have two ropes that burn in exactly 1 hour, but do not burn evenly (so half of the rope does not burn in 30 minutes). How do you measure a 45 minute time period by burning the ropes?


#2
There are four kids on one side of a bridge with one flashlight and can cross in the times below:

Alex can cross the bridge in one minute
Bobby can cross the bridge in two minutes
Charlie can cross the bridge in five minutes
David can cross the bridge in ten minutes

If the kids can only cross one or two at a time, and must have the flashlight with them when they cross, how can all four get to the other side of the bridge in seventeen minutes?


Answer in the comments.
And in case you aren't thinking, SPOILER ALERT: answers will be in the comments.

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