What is the correct answer?


A man can row 40km upstream and 55km downstream in 13 hours also, he can row 30km upstream and 44km downstream in 10 hours. Find the speed of the man in still water and the speed of the current.

A. 5 km/hr

B. 4 km/hr

C. 3 km/hr

D. 1km/hr

Correct Answer :

C. 3 km/hr

let rate upstream=x km/hr and rate downstream=y km/hr.

Then, 40/x +55/y =13… (i) and 30/x +44/y =10

Multiplying (ii) by 4 and (i) by 3 and subtracting, we get:11/y=1 or y=11.

Substituting y=11 in (i),we get:x=5.

Rate in still water =1/2(11+5)kmph=8kmph.

Rate of current=1/2(11-5)kmph=3kmph