Question

A student must leave for campus in 10 minutes or he will be late for class. Unfortunately, heis snowed in. He can shovel the driveway in 20 minutes, and his brother claims to be ableto do it in 18 minutes. If they shovel together, how long will it take to clear the driveway?Will this give enough time for the student to get to the campus?

Answer 1

Make the time it will take them be x

So

$\begin{gathered} \frac{x}{20}\text{ + }\frac{x}{18}\text{ = 1 ( }1\text{ means the driveway clear)} \\ \\ \frac{9x\text{ + 10x }}{180}\text{ = 1} \\ 9x\text{ + 10x = 180} \\ 19x\text{ = 180} \\ \text{divide through by 19} \\ x\text{ = }\frac{180}{19}\text{ = 9.5 minutes} \end{gathered}$

it will take them 9.5 minutes and it will be enough to get to campus