A box contains 15 green and 10 yellow balls. If 10 balls are randomly drawn, one by one, with replacement,…
A box contains 15 green and 10 yellow balls. If 10 balls are randomly drawn, one by one, with replacement, then the variance of the number of green balls drawn is
6
4
$\frac{6}{25}$
$\frac{12}{5}$
Solution
Probability of green ball $(p)=\frac{15}{25}=\frac{3}{5}$
Probability of yellow ball $(q)=\frac{10}{25}=\frac{2}{5}$
Also, $\mathrm{n}=10$
$\begin{aligned}
\therefore \quad \text { Variance } & =\mathrm{npq} \\
& =10\left(\frac{3}{5}\right)\left(\frac{2}{5}\right)=\frac{12}{5}
\end{aligned}$