Question

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 :

• A. 6
• B. 4
• C. $\frac{6}{25}$
• D. $\frac{12}{5}$

Answer 1

Answer: (D)

$\frac{12}{5}$

Answer 2

$n = 10$
p(Probability of drawing a green ball) $=\frac{15}{25}$
$\therefore p=\frac{3}{5}, q=\frac{2}{5}$
var(X) = n.p.q
$=10. \frac{6}{25}=\frac{12}{5}$