1958 AMC 12 Question 28 - thichhoctoan.com

Question 28

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:

$\dfrac14$
$\dfrac{81}{256}$
$\dfrac{27}{64}$
$\dfrac{37}{64}$
$\dfrac{175}{256}$