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: If the operation ∆ is defined by a ∆ b = (b - a)^2/a^2 for all numbers a and b, and a ≠ 0, then what is the result when we evaluate this expression: (-5) ∆ (5 ∆ −5) ?

 Option A: 49/9

 Option B: 49/16

 Option C: 81/16

 Option D: 81/25

 Option E: 100/81
answer:
Option D


question:
Question: Three number are in the ratio 5:6:7. The sum of its largest and smallest numbers equals the sum of the third number and 48. Find the third number?

 Option A: 87

 Option B: 57

 Option C: 48

 Option D: 26

 Option E: 28
answer:
Option C


question:
Question: Walking at 5/6th of its usual speed a cab is 15mnts late. Find its usual time to cover the journey?

 Option A: 25m

 Option B: 45m

 Option C: 32m

 Option D: 75m

 Option E: 62m
answer:

Option D