Question

Alvin paddled for 2 hours with a 5-km/h current to reach a campsite. The returntrip against the same current took 7 hours. Find the speed of the boat in stillwater.

Answer 1

Given:

Alvin paddled for 2 hours with a 5-km/h current to reach a campsite.

Let n be the speed of boat.

Distance is calculated as,

`\begin{gathered} d=rt \\ d=2\mleft(n+5\mright) \end{gathered}`

The return trip against the same current took 7 hours.

`\begin{gathered} d=rt \\ d=7(n-5) \end{gathered}`

Equate both the equations,

`\begin{gathered} 2(n+5)=7(n-5) \\ 2n+10=7n-35 \\ 7n-2n=10+35 \\ 5n=45 \\ n=(45)/(5) \\ n=9 \end{gathered}`

Answer: the speed of the boat is 9 mph.