Question

John has a boat that will travel at the rate of 15 kph in still water. He can go upstream for 35 km in the same time it takes to go 140 km downstream. How fast is his boat traveling when he goes downstream?

Answer 1

The boat traveling at 24 kph when John goes downstream.

Explanation:

We are given the following in the question:

John has a boat that will travel at the rate of 15 kph in still water.

Let x be the speed of the current.

Speed of boat in upstream

`(15-x)\text{ kph}`

Speed of water in downstream

`(15+x)\text{ kph}`

Relation:

`\text{Speed} = \frac{\text{Distance}}{\text{Time}}`

We have to find the speed of boat in downstream.

Time to travel upstream for 35 km = Time to travel 140 km downstream

`\displaystyle(35)/(15-x)=(140)/(15+x)\\\\35(15+x) = 140(15-x)\\525 + 35x = 2100 - 140x\\175x = 1575\\x = 9`

Thus, speed of current is 9 kph.

Speed of boat in downstream = 15 + 9 = 24 kph.

Thus, the boat traveling at 24 kph when John goes downstream.