Question

A 40% antifreeze solution is to be mixed with a 70% antifreeze solution to get 240 liters of a 64% solution. How many liters of the 40% and how many liters of the 70% solutions will be used?

Answer 1

We have 40% antifreeze and 70% antifreeze and we need to make 240 liters of 64% antifreeze.

We set up 2 equations where "f" is the 40 % and "s" is the 70%

A) f + s = 240

B) .40f + .70s = (.64 * 240) (or 153.6)

To solve both equations we multiply A) by -.40

A) -.40 f - .40 s = -96.00 then we add this to B)

B) .40f + .70s = 153.60

.30s = 57.6

s = 192

f = 48

48 liters of 40% = 19.20 liters of antifreeze

192 liters of 70% = 134.40 liters of antifreeze

That equals 153.60 liters of antifreeze in a TOTAL liquid amount of 240 liters.

Double Check

153.60 / 240 = 64% antifreeze.

Explanation: