The quantities in the proportion you give add to 16 pounds, of which 2 pounds are cement. That is, cement constitutes 1/8 of the total weight.
For each yard of concrete, 4000 lb/8 = 500 lb of cement are used.
For 12.5 yards of concrete, 12.5 * 500 = 6,250 pounds of cement will be used.
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"yard" in this case is shorthand for "cubic yard".
This is linear. 8x-5y=15
-5y=15-8x
Divide -5
Y=8/5x-3.
Start at -3 on y axis and go down 8 points and right 3.
10% = 0.1
10% of 5 = 10% x 5 = 0.1 x 5
therefore, the answer is $0.50
K · ( 0, 0 ) = ( 0 , 0 )
k · ( 0 , 4 ) = ( 0 , 10 )
k · ( 6, 0 ) = ( 15, 0 )
k = 15/6 = 10/4 = 2.5
The answer would be: 2.5
