Question

A mixture of concrete is made up of sand and cement in a ratio of 4:5. How many cubic feet of each are needed to make 135 cubic feet of concrete mix?

Answer 1

`60` cubic feet of sand
`75` cubic feet of cement

Explanation:

So we have a ratio of `4 " parts sand" :5 " parts cement"`

so if we take x as some amount where the ratio is true and it totals to 135 cubic feet,

`135=5x+4x`

`135=9x`

`x=15`

or one unit is 15 cubic feet.

so the amount of sand is `4x`

`4(15)=60` cubic feet of sand

The amount of concrete is `5x`

`5(15)=75` cubic feet of cement.

and then to check,

`60+75=135` cubic feet