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
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Q: Question: The bankerâ€™s discount on Rs. 1600 at 10% per annum is the same as true discount on Rs. 1680 for the same time and at the same rate. The time is :

 Option A: 2 months

 Option B: 4 months

 Option C: 6 months

 Option D: 7 months

 Option E: None

A: Option C
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Q: Question: If x is an odd negative integer and y is an even integer, which of the following statements must be true?
I. (3x - 4y) is odd
II. xy^2 is an even negative integer
III. (y^2 - x) is an odd negative integer

 Option A: (3X-4Y

 Option B: II only

 Option C: I and II

 Option D: I and III

 Option E: II and III

A:
Option A
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