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: Machine P and Machine Q are each used to manufacture 770 sprockets. It takes Machine P 10 hours longer to produce 770 sprockets than Machine Q. Machine Q produces 10% more sprockets per hour than Machine A. How many sprockets per hour does Machine A produce?

 Option A: 3

 Option B: 5

 Option C: 7

 Option D: 9

 Option E: 11
[EX A]: Option C

[EX Q]: Question: The average age of students in section A of 100 students is 20 years and the average age of students in section B of 150 students is 30 years. Find the average age of students in both sections taken together?

 Option A: 26 years

 Option B: 30years

 Option C: 15years

 Option D: 25years

 Option E: 20years
[EX A]: Option A

[EX Q]: Question: Of the final grades received by the students in a certain math course, 1/5 are A's, 1/4 are B's, 1/2 are C's, and the remaining 30 grades are D's. What is the number of students in the course?

 Option A:  80

 Option B:  110

 Option C:  160

 Option D:  600

 Option E:  400
[EX A]:
Option D