Question

Two numbers differ by 3. The sum of the greater number and twice the smaller number is 15. Find the smaller number?

Answer 1

Let the greater number be x

let the smaller number be y

By the first condition,

x – y = 3     ....(1)

By the second condition,

x + 2y = 15   ....(2)

Multiply equation (1) with 2

2x – 2y = 6  ....(3)

Adding equation (3) and (2)

  2x – 2y = 6
+  x + 2y = 15  
           3x = 21

x = `21/3`

x = 7

Substituting x = 7 in equation (2)

x + 2y = 15

7 + 2y = 15

2y = 15 – 7

2y = 8

y = `8/2`

y = 4

The smaller number is 4.