If a boat goes upstream for 3 hours, it covers same distance as when it goes downstream for 2 hours. What is the ratio of speed of boat in still water to speed of stream?

A 3 : 1

B 4 : 1

C 5 : 1

D 7 : 2

E 9 : 4

Correct Answer: Option C

Let the speed of stream be V km/hr and speed of boat in still water be U km/hr.

Upstream speed = (U – V) km/hr

Downstream speed = (U + V) km/hr

Distance covered upstream in 3 hours = Distance covered downstream in 2 hours

⇒ 3(U – V) = 2(U + V)

⇒ 3U – 3V = 2U + 2V

⇒ U = 5V

⇒ U/V = 5 : 1

∴ Ratio of speed of boat in still water to speed of stream is 5:1.