This is a very nice lateral thinking problem I picked up from this wonderful collection of puzzles (http://gurmeet.net/puzzles/).
Rajeev is trapped atop a building 200m high. He has with him a rope 150m long. There is a hook at the top where he stands. Looking down, he notices that midway between him and the ground, at a height of 100m, there is a ledge with another hook. In his pocket lies a Swiss knife. Hmm… how might he be able to come down using the rope, the two hooks and the Swiss knife?
As always, please send me answers directly at email@example.com