Discussion
A man takes twice as long to row a distance against the stream as to row the same distance in favour of the stream. The ratio of the speed of the boat (in still water) and the stream is:
Answer: B
Write \( b \) for the boat's speed in still water and \( r \) for the stream's. Then
\[ \text{downstream} = b + r, \qquad \text{upstream} = b - r \]
Twice the time means half the speed over the same distance:
\[ \frac{b + r}{b - r} = 2 \quad\Longrightarrow\quad b + r = 2b - 2r \]
\[ 3r = b \quad\Longrightarrow\quad \frac{b}{r} = 3 \quad\Longrightarrow\quad 3 : 1 \]
Checking with \( b = 3 \) and \( r = 1 \): downstream 4 and upstream 2, so the upstream leg does take twice as long. Neither distance nor actual speed is needed - only the ratio.
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