A class of 27 students is split between boys and girls in the ratio of 5:4.

What's the probability of picking two boys?

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### Solution

The ratio is in nine parts, so each part is $\frac{27}{9}=3$ students.

Therefore the class has $5\times 3=15$ boys.

The probability the first student picks is a boy is $\frac{15}{27}$ and the second is $\frac{14}{26}$.

So the probability of two boys being picked, at random, is $$\frac{15}{27}\times \frac{14}{26}=\frac{35}{117}$$

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