Question

A crew of highway workers paved `2/15` mile in 20 minutes. If they work at the same rate, what portion of a mile will they pave in one hour?

Answer 1

`2/5` of a mile

Explanation:

The easiest approach is to realise that one hour is 3 times longer than `20` minutes. The longer the time, the more they will pave.

`2/15` of a mile, in 20 minutes, how much in 60 minutes?#

They will pave 3 times more.

`2/15 xx 3/1 = 6/15` of a mile

`6/15 = 2/5` of a mile

You could also use the 'unitary method' where you find out how much they pave in ONE minute (divide by `20`) and them multiply by `60` to find how much in one hour.

Look at what happens:

`2/15 div 20 xx 60`

`=2/15 xx1/cancel20 xxcancel60^3`

`= 2/15 xx3" "larr` exactly the same maths.

`=2/5`

Answer 2

There are `60/20=3` periods of 20 minutes in one hour

Explanation:

So they would pave `3xx2/15=(cancel3xx2)/(cancel3xx5)=2/5` mile/hr.