Question

Find all pairs of consecutive odd natural numbers, both of which are larger than 10, such that their sum is less than 40.

Answer 1

Let x be the smaller of the two consecutive odd natural number, so that the other one is x + 2. 

Given x > 10 and x + (x + 2) < 40 

⇒ 2x < 38 

⇒ x < 19 

∴10 < x < 19 

Since x is an odd number, x can take the values 11,13, 15 and 17. 

∴ Required possible pairs are (11, 13), (13, 15), (15, 17), (17,19).

Comments

Thanks for the answer