ArithmeticA boat running upstream takes 8 hours to cover a certain distance while it takes 5 hours to cover the same distance running downstream. What is the ratio between the speed of boat and the speed of water current respectively?

A boat running upstream takes 8 hours to cover a certain distance while it takes 5 hours to cover the same distance running downstream. What is the ratio between the speed of boat and the speed of water current respectively?

A
13:8
B
8:13
C
3:13
D
13:3

Solution:

Solution: Speed of the boat in still water = x

Speed of current = y

So,

$8 (x - y) = 5 (x + y)$

$8 x - 8 y = 5 x + 5 y$

$8 x - 5 x = 5 y + 8 y$

$3 x = 13 y$

$\frac{x}{y} = 13 : 3$