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?

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Answer 1 · 2016-10-26T06:57:10

#60# cubic feet of sand
#75# cubic feet of cement

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