Question

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

• A. $4$
• B. $6$
• C. $3$
• D. $8$

Answer 1

Answer: (A)

$4$

Answer 2

Let x and $x + 2$ be two odd natural numbers. we have, $x > 10\, ? and$x + (x + 2) < 40, ? On solving (i) and (ii), we get $10 < x < 19$ So, required pairs are $(11, 13), (13, 15), (15, 17)$and $(17, 19)$