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: A man’s speed with the current is 18 km/hr and the speed of the current is 2.5 km/hr. the man’s speed against the current is :

 Option A: 8.5 km/hr

 Option B: 9.5 km/hr

 Option C: 13 km/hr

 Option D: 12.5 km/hr

 Option E: None of these
Option C

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
Option D

Question: There r 4 prime numbers in ascending order. The multiplication of first 3 is 385 and that of last 3is 1001. what is the last number is

 Option A: 10

 Option B: 12

 Option C: 11

 Option D: 13

 Option E: 15

Option D