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: Bat is bought for Rs.400 and sold at a gain of 20% find its selling price?

 Option A: Rs.320

 Option B: Rs.350

 Option C: Rs.370

 Option D: Rs.480

 Option E: None of these
[A]: Option D


[Q]: Question: Look at this series: 15, 15, 27, 27, 39, 39, 51, 51, 63, 63, ? ... What number should fill the blank?

 Option A: 51

 Option B: 39

 Option C: 75

 Option D: 15

 Option E: None
[A]: Option C


[Q]: Question: A train crosses a bridge of length 1500 m in 70 seconds and a lamp post on the bridge in 20 seconds. What is the length of the train in metres?

 Option A: 375 m

 Option B: 750 m

 Option C: 250 m

 Option D: 600 m

 Option E: 300 m
[A]:
Option D