Question
In a class, the ratio of number of boys to number of
girls is 9:4. If 5 boys joined the class and 1 girl left the class, then the ratio becomes 7:3. Find the actual number of girls in the class.Solution
Let initially the number of boys and girls be 9x and 4x, respectively.
(9x + 5) : (4x − 1) = 7 : 3
Or, 3(9x + 5) = 7(4x − 1)
Or, 27x + 15 = 28x − 7
Or, x = 22
Therefore, number of girls = 4 × 22 = 88
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