Tuesday, May 11, 2010

Count 45 minutes using rope

Given 2 non-uniform ropes (each burns down in 1hr, but not uniformly), how to measure 45 mins?

Answer : Take one rope connect both ends. Ignite the connection point and one end of the other rope at the same time. When the looped rope burns out, it is 30 mins. Then ignite the unburned end of the remaining rope. When the remaining rope burns out, it is another 15 mins. So it is 45 mins.

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