SOLUTION: How much of a 40% antifreeze solution must a mechanic mix with an 80% antifreeze solution if 20 gallons of a 50% antifreeze solution are needed? Here's what I tried: Let x= a

Algebra ->  Algebra  -> Matrices-and-determiminant -> SOLUTION: How much of a 40% antifreeze solution must a mechanic mix with an 80% antifreeze solution if 20 gallons of a 50% antifreeze solution are needed? Here's what I tried: Let x= a      Log On

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 Click here to see ALL problems on Matrices-and-determiminant Question 607388: How much of a 40% antifreeze solution must a mechanic mix with an 80% antifreeze solution if 20 gallons of a 50% antifreeze solution are needed? Here's what I tried: Let x= amount of 40%, y= amount of 80% 0.40x + 0.80y = 0.5(20) x + y = 20 Multiplied by 10 to get rid of decimals in first equation: 4x + 8y = 10 x + y = 20 Put into matrices and got: (37.5, -17.5) The answer is supposed to equal to 15 gal of 40%, 5 gal of 80% according to the lab worksheet I'm working on. I don't know what I am doing wrong.Answer by ewatrrr(10682)   (Show Source): You can put this solution on YOUR website! ``` Hi Let x= amount of 40%, y= amount of 80% 0.40x + 0.80y = 0.5(20) x + y = 20 OR x = 20-y good Work! substituting (20-y) for x 0.40(20-y) + 0.80y = 0.5(20) .40y = .5(20)-.40(20) y = .10(20)/.40 y = 5 gal of the 80% solution and 15gal of the 40% solution (5 + 15 = 20) ```