Question

A boat running upstream takes $9$ hours to cover a certain distance, while it takes $4$ hours to cover the same distance running downstream. What is the ratio between the speed of the boat and speed of the water current respectively?

• A. $8:3$
• B. $13:5$
• C. $2:1$
• D. $4:3$

Answer 1

The correct option is B $13:5$

Let the speed of boat be $x$ kmph and speed of water current be $y$ kmph.
Then, downstream speed of boat $=(x+y)$ kmph
and upstream speed of boat $=(x-y)$ kmph

Distance covered upstream in $9$ hours $=$ Distance covered downstream in $4$ hours
$\Rightarrow (x-y)\times 9=(x+y)\times 4$
$\Rightarrow 5x=13y$
or, $x:y=13:5$