A man can row three-quarters of a kilometer against the stream in 11 ¼ minutes and return in 7 ½ minutes. The speed of the man in still water is________?

A. 2km/hr
B. 3km/hr
C. 4 km/hr
D. 5 km/hr
Explanation:
Distance covered upstream in 45/4min =3/4 km
Distance covered upstream in 1 hr =(3/4 × 2/15 × 60) km/hr = 4 km/hr
Distance covered downstream in 15/2 min = ¾ km
Distance covered downstream in 1hr
= (3/4 × 2/15 × 60)km/hr = 6 km/hr
Speed of the man in still water
= ½ (6 + 4)km/hr = 5 km/hr