The speed of a boat downstream is 2.5 times its speed upstream. If the total time taken by the boat for going 15 km downstream and the same distance upstream is 4 hours, then what is the speed (in km/h) of the boat downstream?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is Option 2 i.e. .
Let upstream speed = x km/h and Downstream speed = 2.5x km/h
15/(2.5x) + 15/x = 14/3
⇒ 6/x + 15/x = 14/3
⇒ x = (21 × 3)/14 = 4.5 km/h
Downstream speed = 2.5 × 4.5 = 11.25 km/h