You are given a math word problem and you are supposed to make use of mathematical concepts like probability, combinatorics, linear equations, sequences/series, or simple operators like addition, subtraction, division, or multiplication to answer the given question. Choose the best option from the 5 given options and report that option.

Question: Pipe A can fill a tank in 16 minutes and pipe B cam empty it in 24 minutes. If both the pipes are opened together after how many minutes should pipe B be closed, so that the tank is filled in 30 minutes?

 Option A: 20

 Option B: 16

 Option C: 24

 Option D: 28

 Option E: 21
Option E

Question: In a poll of 44,000 dentists, only 30 percent responded; of these, 20 percent claimed to prefer Toothpaste A. How many of the dentists who responded did not claim a preference for Toothpaste A?

 Option A: 2,200

 Option B: 2,640

 Option C: 6,160

 Option D: 8,800

 Option E: 10,560
Option E

Question: David is 18 years older than his daughter Rosy. In 6 years David will be twice as old as Rosy. What is Rosy current age.

 Option A: 12

 Option B: 14

 Option C: 18

 Option D: 24

 Option E: 23

Option A