SOLUTION: The minimum standard for a shipment of gravel is that 85 percent of the gravel should drop through a screen of a certain size. One load of 6 cubic yard testes at only 65 percent. H

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Question 880754: The minimum standard for a shipment of gravel is that 85 percent of the gravel should drop through a screen of a certain size. One load of 6 cubic yard testes at only 65 percent. How much gravel testing at 90 percent must be added to the 65 percent load to make it acceptable?
Thanks.
Answer by josgarithmetic(39629) About Me  (Show Source):
You can put this solution on YOUR website!
Mixture Problem using percents.

Assigning variables,
Q = 6 cubic yards of gravel
L = 65, % which falls through screen
T = 85, % which needs to fall through screen
H = 90, % which can fall through screen, the quality of material to add
y = volume of the H material to add to reach T

Develop this equation.
highlight%28%28LQ%2BHy%29%2F%28Q%2By%29=T%29.
Solve this symbolically for y.
Substitute the assigned other variable values.
Compute y.

Here is a full lesson on this kind of mixture problem:
Mixture: one material quantity unknown