Question

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

• A. $(11,13),(13,15),(15,17),(19,21)$
• B. $(9,11),(13,15),(15,17),(17,19)$
• C. $(11,13),(13,15),(15,17),(17,19)$
• D. $(11,13),(13,15),(15,17),(21,23)$

Answer 1

The correct option is C $(11,13),(13,15),(15,17),(17,19)$

Only C satisfies the conditions mentioned in the question.
In A and D set (19,21) has sum equal to 40. But the sum should be less than 40.
In B set (9,11) has 9 which is less than 10.