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: Two pipes A and B can fill a tank in 15 min and 20 min respectively. Both the pipes are opened together but after 4 min, pipe A is turned off. What is the total time required to fill the tank?

 Option A: 14 min 19 sec

 Option B: 14 min 42 sec

 Option C: 14 min 20 sec

 Option D: 14 min 40 sec

 Option E: 14 min 10 sec
[EX A]: Option D

[EX Q]: Question: In how many different number of ways 6 men and 4 women can sit on a shopa which can accommodate persons?

 Option A: 200

 Option B: 210

 Option C: 90

 Option D: 250

 Option E: 270
[EX A]: Option C

[EX Q]: Question: A man swims downstream 72 km and upstream 45 km taking 9 hours each time; what is the speed of the current ?

 Option A: 2.5 kmph

 Option B: 6.5 kmph

 Option C: 1.5 kmph

 Option D: 8.5 kmph

 Option E: 1.7 kmph
[EX A]:
Option C