Question
Ratio of number of boys to girls in a school is 5:7
respectively. Next year, 50 boys and 70 girls left the school and 250 boys and 280 girls joined the school. If ratio becomes 3:4, then find number of boys now.Solution
Let the initial number of boys and girls be '5n' and '7n' respectively. (5n - 50 + 250) :(7n - 70 + 280) = 3:4 Or, 4 X (5n + 200) = 3 X (7n + 210) Or, 20n + 800 = 21n + 630 Or, 'n' = 170 Required number of boys = 5 X 170 - 50 + 250 = 1050
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