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: The functions f and g are defined for all the positive integers n by the following rule: f(n) is the number of perfect squares less than n and g(n) is the number of primes numbers less than n. If f(x) + g(x) = 16, then x is in the range:

 Option A: 30 < x < 36

 Option B: 30 < x < 37

 Option C: 31 < x < 37

 Option D: 31 < x < 38

 Option E: 32 < x < 38

SOLUTION: Option C

PROBLEM: Question: A fish can go upstream at 35 kmph and downstream at 55 kmph, and then find the speed of the fish in still water?

 Option A: 45

 Option B: 55

 Option C: 35

 Option D: 65

 Option E: 70

SOLUTION: Option A

PROBLEM: Question: The number of positive integer solutions for the equation x +y +z + t = 15 is

 Option A: 654

 Option B: 584

 Option C: 384

 Option D: 364

 Option E: 394

SOLUTION:
Option D