Question

Find all pairs of consecutive odd natural numbers both of which are larger than 10 and their sum is less than 40

Answer 1

Let the two numbers be x and x + 2

x + x + 2 < 40

⇒ 2x < 38

`(2x)/2 < 38/2`

⇒ x < 19 and x > 10

So x = 11 ⇒ x + 2 = 13

x = 13 ⇒ x + 2 = 15

x = 15 ⇒ x + 2 = 17

When x = 17 ⇒ x + 2 = 19

So the possible pairs are (11, 13), (13, 15), (15, 17), (17, 19)