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

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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

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