Question

Washing his dad's car alone, Matt takes 6 hours. If his dad helps him, then it takes 2 hours. How long does it take Matt's dad to wash the car by himself?

Answer 1

If it takes 6 hours for Matt to wash the car, then he washes at a rate of 1/6 cars per hour:

`\begin{gathered} (1)/(x)=6 \\ x=(1)/(6) \end{gathered}`

Let y be the time in which Matt's dad washes the car and state an equation that describes the situation in which Matt and his dad wash the car together:

`\begin{gathered} (1)/(6)+(1)/(y)=2 \\ (1)/(y)=2-(1)/(6) \\ (1)/(y)=(11)/(6) \\ y=(6)/(11) \end{gathered}`

It means that he washes the car in 6/11 hours (approximately 0.54hours).