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Question 78
In a class, there are equal number of boys and girls. Two students are selected for a game.If the probabilty that the two students are girls is $$\frac{7}{29}$$,then what is the strength of the class?
Solution
Let boys and girls in the class are 'x' each.
Total students = x + x = 2x
Probability of selecting two girls from the class = $$\frac{xC1}{2xC1} = \frac{7/29}$$
$$\frac{[x(x - 1)]}{[2x(x - 1)]} = \frac{7}{29}$$
29(x - 1) = 14(2x - 1)
29x - 29 = 28x - 14
x =15
Strength of class = 2x = 30
