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.

[EX Q]: Question: How much more would Rs.20000 fetch, after two years, if it is put at 20% p.a. compound interest payable half yearly than if is put at 20% p.a. compound interest payable yearly?

 Option A: 482

 Option B: 297

 Option C: 278

 Option D: 298

 Option E: 279
[EX A]: Option A

[EX Q]: Question: A businessman earns $28800 in December, thus decreasing his average annual (January to December) earnings by $1300. His average annual earnings would be
Source: CMAT Preparation

 Option A: $29000

 Option B: $33500

 Option C: $40200

 Option D: $41000

 Option E: $43100
[EX A]: Option E

[EX Q]: Question: Tough and Tricky questions: Ratios
4/5 of a certain class left on a field trip. 1/3 of the students who stayed behind did not want to go on the field trip (all the others did want to go). When another vehicle was located, 1/2 of the students who did want to go on the field trip but had been left behind were able to join. What fraction of the class ended up going on the field trip?

 Option A: 1/2

 Option B: 2/3

 Option C: 13/15

 Option D: 23/30

 Option E: 4/5
[EX A]:
Option C