Question

A chemical company makes two brands of antifreeze. The first brand is 30% pure antifreeze, and the second brand is 75% pure antifreeze. In order to obtain 30 gallons of a mixture that contains 60% pure antifreeze, how many gallons of each brand of antifreeze must be used?

Answer 1

Ok. So we have 2 kinds of antifreeze:

Let's call X = the amount of 20% pure antifreeze needed

Then, 180 - X = amount of 70% antifreeze needed

All together it will make 180 gallons of 40% antifreeze

Remember, the word "of" means multiplication"

So X gallons of 20% antifreeze + (180-X) gallons of 70% = 180 gallons of 40%

So:

.20X + .70(180-X) = .40(180)

.20X + 126 - .70X = 72

54 = .50X

108 = X

So, you need 108 gallons of 20% antifreeze and 72 gallons of 70% antifreeze.

Explanation: