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: In an electric circuit, two resistors with resistances x and y are connected in parallel. If R is the combined resistance of these two resistors, then the reciprocal of R is equal to the sum of the reciprocals of x and y. What is R if x is 5 Ohms and y is 7 Ohms?

 Option A: 3/5

 Option B: 1/7

 Option C: 12/35

 Option D: 31/12

 Option E: 35/12
Option E

Question: The average age of 3 boys is 15 years and their ages are in the proportion 1:2:3. The age of the youngest boy is?

 Option A: 10 years

 Option B: 12 years

 Option C: 15 years

 Option D: 18 years

 Option E: 7.5 years
Option E

Question: The circumferences of two circles are 264 meters and 352 meters. Find the difference between the areas of the larger and the smaller circles?

 Option A: 1877 sq m

 Option B: 1976 sq m

 Option C: 4312 sq m

 Option D: 1987 sq m

 Option E: 1678 sq m

Option C