Difficulty: Medium
Correct Answer: 6
Explanation:
Introduction / Context:Mixture (weighted average) problems with two groups can be solved by equating total ages computed from averages. Once the number of women is known, subtract married to get unmarried.Given Data / Assumptions:
Concept / Approach:Total age = average * count. If w is women count, set 16*8 + 22*w = 15*(16 + w) and solve for w. Then unmarried = w - married.Step-by-Step Solution:
Children total = 16 * 8 = 128Women total = 22 * wOverall total = 15 * (16 + w) = 240 + 15wEquation: 128 + 22w = 240 + 15w7w = 112 ⇒ w = 16Unmarried women = 16 - 10 = 6Verification / Alternative check:Totals: 128 + 22*16 = 128 + 352 = 480; group size = 32; 480/32 = 15, consistent.Why Other Options Are Wrong:
Common Pitfalls:Forgetting to multiply averages by group sizes or mixing up the subtraction of married from total women.Final Answer:
6
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