Question
The mean age of 27 students is 13 years. The boys’ average is (b + 3) years and the girls’ average is (b − 6) years. If boys : girls = 4 : 5, determine
b.
Solution
From ratio, Boys = 27 × (4/9) = 12 Girls = 27 − 12 = 15 Equation, 12(b + 3) + 15(b − 6) = 27 × 13 12b + 36 + 15b − 90 = 351 27b − 54 = 351 27b = 405 b = 15
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