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: One-tenth of the students at a nursery school are 4 years old or older. If 20 students have not yet reached their third birthday, and a total of 50 students are not between 3 years old and 4 years old, how many children are in the nursery school?

 Option A: 150

 Option B: 300

 Option C: 450

 Option D: 490

 Option E: 620
[A]: Option B


[Q]: Question: There are n arithmetic means between 3 and 45 such that the sum of these arithmetic means is 552. find the value of n.

 Option A: 11

 Option B: 15

 Option C: 17

 Option D: 21

 Option E: 23
[A]: Option E


[Q]: Question: G is the set of the first n positive odd numbers, where n is a positive integer. Given that n > k, where k is also a positive integer, x is the maximum value of the sum of k distinct members of G, and y is the minimum value of the sum of k distinct members of G, what is x + y?

 Option A:  kn

 Option B:  kn + k^2

 Option C:  kn + 2k^2

 Option D:  2kn – k^2

 Option E:  2kn
[A]:
Option E