Question

A bag contains $12$ balls of two different colours, out of which x are white. One ball is drawn at random. If $6$ more white balls are put in the bag, the probability of drawing a white ball now will be double to that of the previous probability of drawing a white ball. Then, the value of x is ___________.

• A. $3$
• B. $4$
• C. $5$
• D. $6$

Answer 1

Answer: (A)

$3$

Total number of balls $=12$

Number of white balls $=x$

Probability of drawing a white ball out $=\frac{x}{12}$

Given that,

$6$ more white balls are added in bag

Number of white balls $=x+6$

Total number of balls $=18$

Probability of drawing a white ball $=\frac{x+6}{18}=2\frac{x}{12}$

$\Rightarrow x+6=3x$

or

$x=3$