Question

How many weeks does it take to empty the lake?

Answer 1

The rate of emptying the lake is -1/8.

The rate of filling the lake is 1/15

Let t be the time in weeks to empty the lake,

Now, add the given rate to get the total rate of emptying of -1/t.

`\begin{gathered} (-1)/(8)+(1)/(15)=-(1)/(t) \\ (-15+8)/(120)=-(1)/(t) \\ -7* t=-120 \\ t=(120)/(7) \end{gathered}`

Thus,

`t=17(1)/(7)`

Therefore, it will take 17 weeks and 1 day to empty the lake.