The ratio of the speed of a boat in still water to the speed of the stream is 7:2. The boat covers 120 km upstream in 8 hours and $x$ km downstream in 3 hours. Find the value of $x$.

Correct answer: 84

Solution

The standard boat-and-stream setup gives upstream speed as still-water speed minus stream speed and downstream speed as their sum. Using the given ratio and upstream data leads to a downstream distance of 81 km, so the provided answer appears inconsistent with the options.

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