Concrete is made by mixing cement, sand, and

gravel in the ratio 5:9:13. How much cement

is nceded to make 324 ft of concrete?

60 ft.

Step-by-step explanation

The fraction of cement on the concrete

= 5 / (5+9+13)

= (5/27) * 324

= 5 * 12

= 60 ft.

60

Step-by-step explanation:

Sum the parts of the ratio, 5 + 9 + 13 = 27 parts

Divide the amount of concrete by 27 to find the value of one part of the ratio.

324 : 27 = 12 ← value of 1 part of the ratio, thus

5 parts = 5 * 12 = 60 ← cement

9 parts = 9 * 12 = 108 ← sand

13 parts = 13 * 12 = 156 ← gravel