Question

A bag contains 16 balls out of which x balls are red and probability of drawing a red ball is p. If 4 red balls are added, then probability of drawing a red ball is $\frac{8}{5}$ p, find the value of x

• A. 4
• B. 8
• C. 6
• D. 3

Answer 1

Answer: (A)

4

$p=\frac{x}{16}$, after addition of 4 red balls, $\frac{8}{5}p=\frac{x+4}{20}$
$\frac{8}{5}\times \frac{x}{16}=\frac{x+4}{20}\Rightarrow 2x=x+4\Rightarrow x=4$