SOLUTION: Please help me to solve this problem. A certain mine yields low-grade oil shale containing 18.0 U.S. gallons of oil per ton of rock, and another mine has shale yielding 30.0 gal

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Question 1054223: Please help me to solve this problem.
A certain mine yields low-grade oil shale containing 18.0 U.S. gallons of oil per ton of rock, and another mine has shale yielding 30.0 gal./ton. How many tons of each must be sent each day to a processing plant that processes 23000 tons of rock per day, so that the overall yield will be 22.0 gal./ton?

18.0 gal./ton=
30.0 gal./ton=

Answer by jorel555(1290) About Me  (Show Source):
You can put this solution on YOUR website!
Let n be the the amount of rock coming from the low-grade shale. Then the rock coming from the high-grade shale would be 23000-n. So:
n/18 + (23000-n)/30 = 23000/22=1045.454545
5n+3(23000-n)=94090.909090909
2n=25090.909090909
n=12545.45454545 tons of low-grade shale;
23000-n=10454.54545454 tons of high-grade shale. ☺☺☺☺