If a boat travels X km upstream in 44 minutes and 2X km downstream in 1 hour 6 minutes, then the speed of the boat in still water is what percent of the speed of the current?

400%
500%
600%
700%

Correct answer: 700%

Solution

Upstream speed is \(X/(44/60)=15X/11\) and downstream speed is \(2X/(66/60)=20X/11\). Let boat speed be \(b\) and stream speed be \(s\); then \(b-s=15X/11\) and \(b+s=20X/11\). Solving gives \(b/s=7\), so the boat’s speed is 700% of the current’s speed.

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