Discussion of Question with ID = 019 under Boats-and-Streams

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Question

The upstream journey of a boat takes 8 times the time it takes it to complete the downstream journey. What is the ratio of the speed of the boat in still water to the speed of the stream?

A

$1{2/7}$.

B

$2{2/3}$.

C

${2/9}$.

D

$3{1/3}$.

Soln.
Ans: a

Let the distance be L and the speed of the boat in still water be u, with v being the speed of the stream. We are given $L/{u - v} = 8 × L/{u + v}$. We can solve this equation for u/v to get u/v = ${8 + 1}/{8 - 1}$ = $1{2/7}$.


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