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: 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

A: Option D
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Q: Question: A shopkeeper sold an book offering a discount of 5% and earned a profit of 30%. What would have been the percentage of profit earned if no discount was offered?

 Option A: 140

 Option B: 120

 Option C: 130

 Option D: 136.8

 Option E: 150

A: Option D
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Q: Question: A certain family has 3 sons: Richard is 6 years older than David, and David is 8 years older than Scott. If in 8 years, Richard will be twice as old as Scott, then how old was David 2 years ago?

 Option A:  8

 Option B:  10

 Option C:  12

 Option D:  14

 Option E:  16

A:
Option C
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