Wednesday, July 1, 2009

Answer: Bridge Crossing

In the river crossing puzzle, the farmer is the only person who could operate the boat. Therefore the solution is to find minimum number of trips the farmer has to make to bring the wolf, the goat and the cabbage to the other side of the river without leaving the wolf and the goat or the goat and cabbage alone.

In this bridge crossing puzzle, however, we know they have to make 5 trips altogether, so the question is to find the trips of the shortest time. Read the answer here.

Bridge Crossing

Remember the puzzle of a farmer crossing a river with a wolf, a goat and a cabbage? It is really a question of how the farmer ferries the wolf, goat and cabbage one at a time to the other side of the river without leaving the wolf and goat or the goat and the cabbage alone during the process.

Here is a puzzle of bridge crossing with some time constraints:

Four people A, B, C and D have to cross a bridge at night. The bridge is narrow so it can only allow two persons at a time. Since it is dark they have to use a flashlight when crossing the bridge. The speed of crossing the bridge for A, B, C and D are 1, 2, 5 and 10 minutes respectively. Their flash light can last only 17 minutes.
How do they cross the bridge?