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.

[EX Q]: Question: One water pump can fill half of a certain empty tank in 7 hours. Another pump can fill half of the same tank in 7.5 hours. Working together, how long will it take these two pumps to fill the entire tank?

Option A: 7 7/13

Option B: 1 5/8

Option C: 3 1/4

Option D: 7 7/29

Option E: 3 1/2
[EX A]: Option D

[EX Q]: Question: In an examination, 32% candidates failed in one subject and 42% failed in another subject while 15% failed in both the subjects. If 2500 candidates appeared at the end of the examination how many passed in either subject but not in both?

Option A: 975

Option B: 1020

Option C: 1100

Option D: 1243

Option E: 1525
[EX A]: Option C

[EX Q]: Question: The C.P of 15 books is equal to the S.P of 18 books. Find his gain% or loss%?

Option A: 16 2/3%

Option B: 16 2/8%

Option C: 16 2/5%

Option D: 16 2/1%

Option E: 16 1/3%
[EX A]:
Option A