A man swims from A to B and back in 4.5 hours. A block of wood when allowed to go with the stream from A to B takes 6 hours. What is the ratio of the speed of the man in still water to that of the stream?

A. 2 : 1

B. 3 : 1

C. 4 : 1

D. 5: 1

B. 3 : 1

$$
\begin
\frac+\frac & =\frac \\
\\
\frac & =6
\end
$$

Substituting d = 6s

$$ \frac+\frac=\frac $$

Rather than solve, use options –

(A) $\frac+\frac=8 \neq 9 / 2$.

(B) $\frac+\frac=4.5$