A man rows 8 km upstream in 4 hours and 16 km downstream in 4 hours. What is the speed of the current?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 1 km/hr
\( \displaystyle \text{Upstream speed } u=\frac{8}{4}=2\text{ km/hr} \)
\( \displaystyle \text{Downstream speed } d=\frac{16}{4}=4\text{ km/hr} \)
If the boat’s speed in still water is b and the current’s speed is c, then u = b − c and d = b + c. Subtracting, the speed of the current is half the difference:
\( \displaystyle c=\frac{d-u}{2} \)
\( \displaystyle =\frac{4-2}{2}=1\text{ km/hr} \)
CBSE Applied Mathematics (Class XII):
Boats and Streams
