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.

[Q]: Question: Two pipes A and B can fill a cistern in 20 and 30 minutes respectively, and a third pipe C can empty it in 40 minutes. How long will it take to fill the cistern if all the three are opened at the same time?

 Option A: 17 1/5

 Option B: 17 1/8

 Option C: 17 1/7

 Option D: 17 1/1

 Option E: 17 1/2
[A]: Option C


[Q]: Question: Find the fourth proportion to 2,4,6

 Option A: 18

 Option B: 12

 Option C: 9

 Option D: 6

 Option E: 8
[A]: Option B


[Q]: Question: If 4 (A's capital) = 6 (B's capital) = 10 (C's capital), then out of a profit of Rs. 4650, C will receive ?

 Option A: Rs.980

 Option B: Rs.228

 Option C: Rs.900

 Option D: Rs.287

 Option E: Rs.921
[A]:
Option C