Question

Find all pairs of consecutive even positive integers, both of which are larger than 5 such that their sum is less than 23.

Answer 1

Let x be the smaller of the two consecutive even positive integers. Then, the other integer is x + 2.

Since both the integers are larger than 5,

x > 5 ... (1)

Also, the sum of the two integers is less than 23.

x + (x + 2) < 23

⇒ 2x + 2 < 23

⇒ 2x < 23 – 2

⇒ 2x < 21

⇒ x < `21/2`

⇒ x < 10.5  ...(2)

From (1) and (2), we obtain 5 < x < 10.5.

Since x is an even number, x can take the values 6, 8, and 10.

Thus, the required possible pairs are (6, 8), (8, 10), and (10, 12).