A boat goes 24 km upstream in 4 hours and 32 km downstream in 4 hours. The speed of the boat in still water is:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 7 km/hr
The speeds against and with the stream are
\( \displaystyle \text{upstream speed}=\frac{24}{4}=6\ \text{km/hr} \)
\( \displaystyle \text{downstream speed}=\frac{32}{4}=8\ \text{km/hr} \)
If u is the speed of the boat in still water and v the speed of the stream, then u − v = 6 and u + v = 8. Adding the two equations:
\( \displaystyle 2u=14 \)
\( \displaystyle u=7\ \text{km/hr} \)
CBSE Applied Mathematics (Class XII):
Boats and Streams
