Question
In a class of students, the ratio of boys to girls is
5:3. If 15 boys and 5 girls join the class, the ratio becomes 9: 5. What was the initial number of boys in the class?Solution
Let the number of boys be 5x and the number of girls be 3x. After joining, the boys = 5x + 15 and girls = 3x + 5. New ratio: (5x + 15) / (3x + 5) = 9/5 Cross-multiplying gives: 5(5x + 15) = 9(3x + 5) 25x + 75 = 27x + 45 2x = 30 x = 15 Initial number of boys = 5x = 75
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