TASK DEFINITION: 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.
PROBLEM: Question: In an office, 20 percent of the workers have at least 5 years of service, and a total of 16 workers have at least 10 years of service. If 90 percent of the workers have fewer than 10 years of service, how many of the workers have at least 5 but fewer than 10 years of service?

 Option A:  32

 Option B:  64

 Option C:  50

 Option D:  144

 Option E:  160

SOLUTION: Option A

PROBLEM: Question: Find compound interest on Rs. 5000 at 12% per annum for 1 year, compounded half-yearly.

 Option A: Rs. 600

 Option B: Rs. 618

 Option C: Rs. 525

 Option D: Rs. 620

 Option E: None

SOLUTION: Option B

PROBLEM: Question: A used-book dealer sells paperback books at 3 times the dealer's cost and hardback books at 4 times the dealer's cost. Last week, the dealer sold a total of 130 books, each of which had cost the dealer $1. If the gross profit (sales revenue minus the dealer's cost) on the sale of all of these books was $300, how many of the books sold were paperbacks?

 Option A: 40

 Option B: 60

 Option C: 75

 Option D: 90

 Option E: 100

SOLUTION:
Option D