Problem: A 16-quart radiator is filled with water. Four quarts are removed and replaced with pure antifreeze liquid. Then four quarts of the mixture are removed and replaced with pure antifreeze. This is done a third and a fourth time. The fractional part of the final mixture that is water is:
Answer Choices:
A. 1/4
B. 81/256
C. 27/64
D. 37/64
E. 175/256
Solution:
RemovalsFirstSecondThirdFourthWater drawn4324111611Water left1296435161Antifreeze drawn011432165Antifreeze left43+4=7541+4=94161615+4=101615
165161=25681
16101615=256175