Question

A boat crew rowed 105 kilometers downstream, with the current, in 5 hours. The return trip upstream, against the current, covered the same distance, and it took 21 hours. Find the crew is rowing rate in still water.rowing rate=_______ kilometers per hour

Answer 1

It's important to notice that downstream indicates that the river goes in the same direction that the boat crew, so we add; while upstream they have opposite directions so we subtract.

First, we find the ratio in each case.

Then, we form the following system

`\begin{gathered} x+y=21 \\ x-y=5 \end{gathered}`

The first equation is with the current and the second one is against. Let's combine the equations and solve for x

`\begin{gathered} x+x+y-y=21+5 \\ 2x=26 \\ x=(26)/(2) \\ x=13 \end{gathered}`

Therefore, the rowing rate in still water is 13 kilometers per hour.