Question

aAlvin paddled for 2 hours with a 7-km/h current to reach a campsite. The returntrip against the same current took 9 hours. Find the speed of the boat in stillwater

Answer 1

Given data:

Alvin paddled for 2 hours with a 7-km/h current to reach a campsite.

The return trip against the same current took 9 hours.

Let Boat speed speed x km/h.

The current speed 7 km/h.

The against current x- 7.

The with current x+ 7.

The time paddles against current 9 hours.

The time paddles with the current is 7 hours.

The Distance is same here,

`Distance=speed\cdot\text{time}`

thus,

`\begin{gathered} 9(x-7)=7(x+7) \\ 9x-63=7x+49 \\ 9x-7x=49+63 \\ 2x=112 \\ x=(112)/(2) \\ x=56 \end{gathered}`

Thus, the speed of the boat in still water is 56 km/h.