Ratio now and gap given: Mona and her mother: Mona : mother = 5 : 15 now (i.e., 1 : 3). Their age difference is 24 years. What will be the ratio of their ages after 3 years?

Introduction / Context:
Given both a ratio and a fixed difference, we can determine actual present ages. Then projecting both ages forward by the same number of years lets us compute the new ratio and compare with options. This tests understanding that ratios typically change when equal years are added.

Given Data / Assumptions:

• Present ratio Mona : mother = 1 : 3.
• Age difference = 24 years.
• Let Mona = x, mother = 3x.

Concept / Approach:
From difference 3x − x = 24 ⇒ 2x = 24 ⇒ x = 12. Then compute both ages after 3 years and reduce the ratio to lowest terms. Finally, match with the most appropriate option.

Step-by-Step Solution:

Verification / Alternative check:
Check the difference after 3 years remains 24 (since both increased by 3), consistent with linear aging.

Why Other Options Are Wrong:
1:3 and 2:3 or 3:7 do not equal 5:13. Hence “None of these” is the only correct choice.

Common Pitfalls:
Assuming the ratio remains 1:3 after adding equal years; that only happens if both ages are scaled by a common factor, not when we add a constant.

Final Answer:
None of these