Twice the difference between two numbers is equal to their sum. If one number is 15, find the other number.

Question

Question

This question was previously asked in

NTPC Tier I (Held On: 30 Mar 2016 Shift 3)

Answer 1

Calculation:

Let the numbers be x and y

According to the question,

2(x – y) = x + y

⇒ 2x - 2y = x + y

⇒ 2x - x = y + 2y

⇒ x = 3y

Since, one of the number is 15

Case (1): If x = 15, so

x = 3y

⇒ 15 = 3y

⇒ y = 15/3 = 5

Case (2): If y = 15, so

x = 3y = 3 × 15 = 45

Thus, the other number is 5 or 45.

Confusion Points

In the question it is asked to find the other number and other numbers may be 5 or 45

It is not asked about the first number so 15 and 45 is not the correct answer.