Question
In a class, the ratio of number of boys to number of
girls is 10:7. If 5 boys joined the class and 3 girls left the class, then the ratio becomes 5:3. Find the actual number of girls in the class.Solution
Let initially the number of boys and girls be 10x and 7x, respectively.
(10x + 5) : (7x − 3) = 5 : 3
Or, 3(10x + 5) = 5(7x − 3)
Or, 30x + 15 = 35x − 15
Or, 5x = 30 ⇒ x = 6
Therefore, number of girls = 7 × 6 = 42Â
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