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.

[Q]: Question: Two trains are moving at 60 kmph and 70 kmph in opposite directions. Their lengths are 150 m and 100 m respectively. The time they will take to pass each other completely is?

 Option A: 5 sec

 Option B: 6 sec

 Option C: 7 sec

 Option D: 8 sec

 Option E: 9 sec
[A]: Option C


[Q]: Question: The average age of 3 boys is 15 years and their ages are in the proportion 1:2:3. The age of the youngest boy is?

 Option A: 10 years

 Option B: 12 years

 Option C: 15 years

 Option D: 18 years

 Option E: 7.5 years
[A]: Option E


[Q]: Question: The mass of 1 cubic meter of a substance is 700 kilograms under certain conditions. What is the volume, in cubic centimeters, of 1 gram of this substance under these conditions? (1 kilogram = 1,000 grams and 1 cubic meter = 1,000,000 cubic centimeters)

 Option A: 0.8

 Option B: 1.42

 Option C: 8.0

 Option D: 12.5

 Option E: 80
[A]:
Option B