Question

A builder makes a certain type of concrete by mixing together 1 part portland cement (made from lime and clay), 3 parts sand, and 5 parts crushed stone. If 765 ft^3 of concrete are needed, how many cubic feet of each ingredient does he need?
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Answer 1

Answer:

• 85 ft^3 portland cement
• 255 f^3 sand
• 425 ft^3 crushed stone

Step-by-step explanation:

The total number of parts is 1+3+5 = 9. The relevant fractions of the mix are ...

  1/9 = portland cement

  3/9 = 1/3 = sand

  5/9 = crushed stone

Since the total is 765 ft^3, the ingredients required are ...

  (1/9)(765 ft^3) = 85 ft^3 portland cement

  (1/3)(765 ft^3) = 255 f^3 sand

  (5/9)(765 ft^3) = 425 ft^3 crushed stone