Question
Four years ago, the average age of A, B and C was 24
years. At present, the ratio of the ages of A and B is 3 : 2, and C is 4 years older than A. What is the present age of B?Solution
ATQ, Four years ago: Average age = 24 → sum = 24 × 3 = 72 Let present ages: A = a, B = b, C = c Then (a – 4) + (b – 4) + (c – 4) = 72 ⇒ a + b + c – 12 = 72 → a + b + c = 84 …(1) Given: a : b = 3 : 2 → a = 3k, b = 2k Also c = a + 4 = 3k + 4 From (1): 3k + 2k + (3k + 4) = 84 ⇒ 8k + 4 = 84 → 8k = 80 → k = 10 So B’s present age = b = 2k = 20 years.
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