Question

A man can row three-quarters of a kilometre against the stream in 45/4 minutes and down the stream in 15/2 minutes. The speed (in km/hr) of the man in still water is: 

a) 2 

b) 3 

c) 4 

d) 5

Answer 1

Correct option: d) 5

Explanation:

Rate upstream= (750/675) m/sec =10/9 m/sec tare downstream=(750/450) m/sec =5/3 m/sec

Rate in still water=1/2*((10/9) +(5/3)) m/sec =25/18 m/sec =((25/18)*(18/5)) km/hr = 5 kmph