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: 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
[A]: Option D


[Q]: Question: In the class of 100 students, 50 speak Hindi and 70 speak English. What is the lowest possible number of students who
speak both the languages?

 Option A: A

 Option B: B

 Option C: C

 Option D: D

 Option E: E
[A]: Option C


[Q]: Question: A train crosses a platform of 120 m in 15 sec, same train crosses another platform of length 180 m in 18 sec. then find the length of the train?

 Option A: 297m

 Option B: 276m

 Option C: 267m

 Option D: 180m

 Option E: 287m
[A]:
Option B