A car radiator contains 20 quarts of a 20 antifreeze solutio

A car radiator contains 20 quarts of a 20% antifreeze solution. How many quarts will have to be removed/ replaced with pure antifreeze to obtain a 50% solution. Assign variables and write an equation.

Solution

Let x = amount that has to be removed/ replaced with pure antifreeze

antifreeze left + added antifreeze= antifreeze in new mixture

0.20 (20-x) + x = 0.50 (20)

4 - 0.2x + x = 10

4 + 0.8 x = 10

0.8 x =6

x = 6/0.8 = 7.5 quarts