Question

A river 2 km wide is flowing at the rate of 2km/hr. A boatman, can row the boat at a speed of 4 km/hr in still water, goes a distance of 2 km upstream and them comes back. The time taken by him to complete his journey is
A. 60 minutes
B. 70 minutes
C. 80 minutes
D. 90 minutes

Answer 1

Correct Answer - C
The velocity upstream is `(4-2)` km/hr nd downstream is (4+2) km/hr.
`therefore "Total time taken"=(2km)/(2km//hr)+(2km)/(6km//hr)`
`=80` minutes