A man rows his boat 525 m in 250 seconds along the stream and returns in 7 minutes. The rowing speed in still water (in km/h) is:
Show answer & explanation
Correct answer: B
Explanation
The correct answer is Option 2 i.e. 5.88 km/h.
Speed of boat along the stream = x + y
Speed of boat against the stream = x - y
Where x and y are the speed of the boat and the speed of the stream
According to the question;
Speed of boat along the stream:
x + y = 525/250 = 2.1 m/s or
⇒ 2.1 × 18/5 = 7.56 km/h ----- (1)
Speed of boat against the stream:
x - y = 525/450 = 1.16 m/s or
⇒ 1.16 × 18/5 = 4.2 km/h ----- (2)
Adding both equations (1) and (2), we get:
⇒ 2x = 7.56 + 4.2
⇒ x = 5.88 km/h
Hence,
Rowing speed in still water = 5.88 km/h