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: The ratio between the speeds of two trains is 7 : 8. If the second train runs 400 kms in 4 hours, then the speed of the first train is:

 Option A: 70 km/hr

 Option B: 75 km/hr

 Option C: 84 km/hr

 Option D: 87.5 km/hr

 Option E: 88.5 km/hr
[EX A]: Option D

[EX Q]: Question: In a T.V. factory, an average of 61TVs are produced per day for the fist 25days of the months. A few workers fellill for the next five daysreducing the daily avg for the month to58 sets/day . The average production per day for day last 5days is ?

 Option A: 35

 Option B: 39

 Option C: 48

 Option D: 50

 Option E: 43
[EX A]: Option E

[EX Q]: Question: A man can do a piece of work in 8days, but with the help of his son, he can finish it in 3days. In what time can the son do it alone?

 Option A: 5

 Option B: 5 1/2

 Option C: 4 4/5

 Option D: 6

 Option E: 9 1/2
[EX A]:
Option C