how many gallons of each brand of antifreeze must be used?

Question

A chemical company makes two brands of antifreeze. The first brand is 65%

 pure antifreeze, and the second brand is 90%

 pure antifreeze. In order to obtain 150

 gallons of a mixture that contains 75%

 pure antifreeze, how many gallons of each brand of antifreeze must be used?

Answer 1

90-75=15

75-65= 10

15/10 = 1.5

90/60 = 1.5

x = .6(150)= 90 gallons of 65%

150-90 = 60 gallons of 90%

.9x + .65(150-x) = .75(150)

.9x -.65x = .75(150)-.65(150)

.25x = .1(150) = 15

x = 15/.25 = 60 gallons of 90%

150-60= 90 gallons of 65%

check the answers:

.9(60)+.65(90)

=54 +58.5

= 112.5

= .75(150)

= 112.5