Question
Average height of 18 boys is 150 cm and average height of 'n' girls is 140
cm. If average height of all the boys and girls is 144 cm, then find the value of (n - 3).
Solution
Sum of height of boys = 18 × 150 = 2700 Sum of height of girls = 140n (2700 + 140n) ÷ (n + 18) = 144 Or, 2700 + 140n = 144n + 2592 Or, 4n = 108 Or, 'n' = 27 Required value = 27 - 3 = 24
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