John likes to have lightly flavored tea every evening. In a 50% strong milk tea, he replaces 15% of it with milk twice. Then, he replaces 10 percent of the resultant solution with more milk.
What is the final concentration of tea John drinks? Pick one.
A) 15.38%  B) 42%  C) 39.86%  D) 22.35%  E) 32.51%
Imagine starting out with 100 ml of 50% milk tea.   In step 1, 15% of the tea is replaced with milk. Thus, 85% of the original tea remains. Since this is done twice, we have a concentration of 50x0.85x0.85% (=36.125%) of tea solution.   Finally, 10% of this solution is replaced with milk again. So, the final concentration of tea is 36.125*0.9%   This equals 32.51% of tea solution.   Answer: 32.51%
<result>E</result>
John likes to have lightly flavored tea every evening. In a 50% strong milk tea, he replaces 15% of it with milk twice. Then, he replaces 10 percent of the resultant solution with more milk.
What is the final concentration of tea John drinks?