A boatman rows 2 km in 10 mins, along the stream and 12 km in 2 hours against the stream. What is the speed of the stream?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is Option 3 i.e. 3 km/h.
A boatman rows 2 km in 10 mins, along the stream and 12 km in 2 hours against the stream.
Let the speed of the boat be x km/h and the stream be y km/h.
Speed = Distance/Time
Along the stream -
Speed (x + y) = 2/(10/60) = 12
⇒ x + y = 12 ...(1
Against the stream -
⇒ x - y = 12/2 = 6
⇒ x - y = 6 ...(2
Subtracting eq(2 from eq(1 -
⇒ (x + y) - (x - y) = 12 - 6
⇒ 2y = 6
⇒ y = 3 km/h