Question

"To make concrete is takes 8 parts crushed gravel, 7 parts water and 5 parts cement mix. A worker needs to make 220kg of concrete. How much crushed gravel, water and cement mix is needed?"
Please show the work, thank you

Answer 1

Ratio of crushed gravel to water to cement mix = 8:7:5 (for a total of 20 parts)

Thus . .
8/20 = fraction of crushed gravel
7/20 = fraction of water
5/20 = fraction of cement mix

If total is 200 kg, then . . .
(8/20)*(200 kg) =  80 kg crushed gravel
(7/20)*(200 kg) =  70 kg water
(5/20)*(200 kg) =  50 kg cement mix

Answer 2

8+7+5=20 
220/20=11
8 x 11=88
7 x 11=77
5 x 11=55