Past 3× and future 2× around today: Five years ago Mayank's mother was three times as old as Mayank. Five years from now she will be twice his age. What is Mayank's present age?
Verbal Reasoning
Problems on Ages
Difficulty: Medium
Choose an option
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A13 years
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B15 years
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C20 years
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D30 years
Answer
Correct Answer: 15 years
Explanation
Introduction / Context:Two symmetric time conditions (−5 and +5) precisely fix the present ages. Translate to equations and solve.
Given Data / Assumptions:
- M = mother's present age; m = Mayank's present age.
- Five years ago: M − 5 = 3(m − 5).
- Five years from now: M + 5 = 2(m + 5).
Concept / Approach:Solve the pair by expressing M from both equations and equating them.
Step-by-Step Solution:1) From past: M = 3m − 10.2) From future: M = 2m + 5.3) Equate: 3m − 10 = 2m + 5 ⇒ m = 15.4) Then M = 2m + 5 = 35.
Verification / Alternative check:Five years ago: 30 vs 10 → 3×. In five years: 40 vs 20 → 2×. Both conditions hold.
Why Other Options Are Wrong:They fail one of the two multiplicative checks upon substitution.
Common Pitfalls:Mishandling the ±5 shift on both ages; both change simultaneously.
Final Answer:15 years