Question

A man can swim at 8 kmph in still water. He covers an equal distance of 18 km both in upstream and downstream between two points in 6 hours. Find the speed of stream .
A. 5 km/h
B. 6 km/h
C. 7 km/h
D. 4 km/h

Answer 1

Correct Answer - D
Let rate of stream is s km/h .
`therefore (18)/((8-s)) + (18)/((8 + s)) = 6 `
`implies 18 xx (8 + s + 8 - s) = 6 (64 - s^(2))`
`implies s^(2) = 16`
`implies s = pm 4`km/h.