SOLUTION: A certain kind of concrete has twice as much sand as cement and five times as much gravel as cement. In 1000 cu. yard of concrete, determine amount of cu. yd. of each material.

Question 983944: A certain kind of concrete has twice as much sand as cement and five times as much gravel as cement. In 1000 cu. yard of concrete, determine amount of cu. yd. of each material.
Let X = cement
Let Y = sand
Let Z = gravel
2Y = X
5G = X
I don't know how to proceed.

Answer by macston(5194) (Show Source): You can put this solution on YOUR website!
.
X=cement; Y=sand=2X; Z=gravel=5X
.
X+Y+Z=1000 cu. yds Substitute for Y and Z.
X+2X+5X=1000 cu yds
8X=1000 cu yds
X=125 cu yds ANSWER 1: There is 125 cu yds of cement.
.
Y=2X=2(125 cu yds)=250 cu yds ANSWER 2: There is 250 cu yds of sand.
.
Z=5X=5(125 cu yds)=625 cu yds ANSWER 3: There is 625 cu yds of gravel.
.
CHECK:
X+Y+Z=1000 cu yds
125 cu yds+250 cu yds+625 cu yds=1000 cu yds
1000 cu yds=1000 cu yds

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