Difficulty: Easy
Correct Answer: 24 years
Explanation:
Introduction / Context:Average age questions translate to total-sum calculations. A known average times the number of people yields the total of their ages at that time. We compare “three years ago” and “now with a third person” to isolate C’s present age.
Given Data / Assumptions:
Concept / Approach:Convert averages to totals and use aging. From 3 years ago to now, A and B each gain 3 years, so the pair’s sum increases by 6. Subtract to find C’s age.
Step-by-Step Solution:
Sum(A, B) three years ago = 36.Sum(A, B) now = 36 + 3 + 3 = 42.Sum(A, B, C) now = 66 ⇒ C = 66 − 42 = 24.Verification / Alternative check:
If A + B = 42 now, and C = 24, then average now = (42 + 24)/3 = 22 ✔.Why Other Options Are Wrong:
27, 28, 30 do not satisfy totals/averages simultaneously.Common Pitfalls:
Forgetting that both A and B aged 3 years each, adding 6 to the sum.Multiplying averages incorrectly instead of totals.Final Answer:24 years
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