Question

A boatman goes 4 km against the current of the stream in 1 hour and goes 2 km along the current in 10 minutes. How long will it take to go 24 km in stationary water?

• A. 5 hrs
• B. 3 hrs
• C. 2 hrs
• D. 6 hrs

Answer 1

Answer:

B. 3 hrs

Explanation: 

Upstream=$\frac{4}{1}=4 \frac{km}{hr}$

Downstream = $2\times{\frac{60}{10}}=12\frac{km}{hr}$

Speed in still water $=\frac{(12+4)}{2}$

$=\frac{16}{2}=8\frac{km}{hr}$.

For 24 km time $=\frac{24}{8}$

=3hrs.