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: The greatest common factor of 16 and the positive integer n is 4, and the greatest common factor of n and 45 is 3. Which of the following could be the greatest common factor of n and 210?

 Option A: 3

 Option B: 14

 Option C: 30

 Option D: 42

 Option E: 70
[A]: Option D


[Q]: Question: P is three times as fast as Q and working together, they can complete a work in 18 days. In how many days can Q alone complete the work?

 Option A: 24

 Option B: 77

 Option C: 88

 Option D: 55

 Option E: 778
[A]: Option A


[Q]: Question: An equilateral triangle T2 is formed by joining the mid points of the sides of another equilateral triangle T1. A third equilateral triangle T3 is formed by joining the mid-points of T2 and this process is continued indefinitely. If each side of T1 is 50 cm, find the sum of the perimeters of all the triangles.

 Option A: 180 cm

 Option B: 220 cm

 Option C: 240 cm

 Option D: 270 cm

 Option E: 300 cm
[A]:
Option E