Question

A man rows to a place 48 km distant and back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against the stream. the rate of the stream is

• A. 1km/h
• B. 1.5km/h
• C. 1.8km/h
• D. 3.5km/h

Answer 1

Answer: (A)

1km/h

Answer 2

The correct option is (A):Speed of man = $x$ km/hr
Speed of boat = $y$ km/hr
Downstream speed = $(x+y)$km/hr and Upstream speed = $(x-y)$km/hr
Accordingly $\frac{4}{x+y}$=$\frac{3}{x-y}$
$4x-4y=3x=3y$
i.e. $x=7y$ -----(1)
$\frac{48}{x+y}+\frac{48}{x-y}= 14$
$\frac{48}{8y}+\frac{48}{6y}= 14$
$y=1$
$\therefore$ Speed of stream 1km/hr