### Brain Teasers

# Solution Problem

A truck had a 14-quart coolant system that contained a 45% antifreeze solution. How many quarts of this solution would have to be drained and replaced with pure antifreeze to achieve a 75% antifreeze solution in the truck?

### Answer

Set up the problem as an equation.Antifreeze left after draining = 45% *(14 - x)

Antifreeze replaced = x

Final amount of antifreeze = .75 * 14 = 10.5

So the balance is:

Antifreeze left after draining + Antifreeze replaced = Final amount of antifreeze

.45(14 - x) + 1x = 10.5

6.3 - .45x + x= 10.5

.55x = 4.2

x = 7.64 quarts

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