A radiator contains 20 liters of a mixture which is 40% antifreeze. You want to drain off and add an equal volume of antifreze to bring the percentage up to 60%. How many liters should you drain off?
40% x 20 = 8 liters of antifreeze 60% x 20 = 12 liters of other mixtures. Let the number of liters to be drained =L 0.4*20 =0.6*[20 - L], solve for L L =20/3 =6 2/3 liters has to be drained and replaced with 6 2/3 liters of 100% antifreeze.
