SOLUTION: If Rio coffee costs $5 a pound and Java cost $7.50 a pound, how many pounds of each must be bought to fill a 120-pound canister with a blend worth $7 a pound?
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-> SOLUTION: If Rio coffee costs $5 a pound and Java cost $7.50 a pound, how many pounds of each must be bought to fill a 120-pound canister with a blend worth $7 a pound?
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Question 1113692: If Rio coffee costs $5 a pound and Java cost $7.50 a pound, how many pounds of each must be bought to fill a 120-pound canister with a blend worth $7 a pound? Answer by ikleyn(52781) (Show Source):
R + J = 120 (1) (R pounds of Rio and J pounds of Java)
5R + 7.50J = 7*120 (2) ("money" equation)
Multiply eq(1) by 5 (both sides). Keep eq(2) as is:
5R + 5J = 5*120 (1')
5R + 7.50J = 7*120 (2')
Subtract eq(1') from eq(2'). In this way, you eliminate R and get a single equation for the unknown J:
7.50J - 5J = 7*120 - 5*120
2.5J = 240 ====> J = = 96.
Answer. 96 pounds of Java coffee and the rest 120-96 = 24 pounds of Rio coffee.
Solved.
On the way, you learned how the Elimination method works.
