instruction:
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.
question:
Question: Two stations A and B are 20 km apart on a straight line. One train starts from A at 7 a.m. and travels towards B at 20 kmph. Another train starts from B at 8 a.m. and travels towards A at a speed of 25 kmph. At what time will they meet?

 Option A: 9

 Option B: 10

 Option C: 11

 Option D: 12

 Option E: 8
answer:
Option E


question:
Question: The population of a certain town increases by 50 percent every 50 years. If the population in 1950 was 810, in what year was the population 160?

 Option A: 1650

 Option B: 1700

 Option C: 1750

 Option D: 1800

 Option E: 1850
answer:
Option C


question:
Question: If x and y are numbers such that (x+5)(y-5)=0, what is the smallest possible value of x^2 + y^2

 Option A: 0

 Option B: 4

 Option C: 9

 Option D: 25

 Option E: 16
answer:

Option D