A boatman finds that his downstream speed is twice his upstream speed. The river flows at 3 km/hr. What is his rowing speed in still water?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 9 km/hr
The downstream speed is more than the upstream speed by twice the river’s speed. Let the upstream speed be \(u\) km/hr; the downstream speed is \(2u\).
\(2u-u=2\times3\), so \(u=6\) km/hr
Downstream speed \(=2\times6=12\) km/hr
Rowing speed in still water \(\displaystyle =\frac{12+6}{2}=9\) km/hr