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.
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Question: 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

Answer: Option C


Question: Question: 23, 18, 16, 11, 9, 4 ?

 Option A: 3

 Option B: 2

 Option C: 7

 Option D: 5

 Option E: 1

Answer: Option B


Question: Question: A walks at 30 kmph and 30 hours after his start, B cycles after him at 40 kmph. How far from the start does B catch up with A?

 Option A: 1200km

 Option B: 1500km

 Option C: 2000km

 Option D: 2500km

 Option E: 3600km

Answer:
Option D