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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