TASK DEFINITION: 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.
PROBLEM: 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

SOLUTION: Option D

PROBLEM: Question: A and B complete a work in 6 days. A alone can do it in 10 days. If both together can do the work in how many days?

 Option A: 3.75

 Option B: 3.76

 Option C: 3.79

 Option D: 3.74

 Option E: 3.71

SOLUTION: Option A

PROBLEM: Question: Find the third proportional to 63 and 29.9?

 Option A: 14.09

 Option B: 14.29

 Option C: 14.19

 Option D: 14.16

 Option E: None of these

SOLUTION:
Option C