The liquid in a car's radiator is 75% water and 25% antifreeze. Suppose that 30% of the radiator's liquid is drained out and replaced with pure antifreeze. What percent of the radiator's liquid is now antifreeze?

Answer 1

suppose the radiator holds 40 cups (10 qts) ... 30 c water , 10 c antifreeze

12 c drained (.30 * 40) ... 9 c water , 3 c antifreeze
... leaving 21 c water and 7 c antifreeze

refilled with antifreeze
... now has 21 c water and 19 c antifreeze

19 / 40 = ? %