Question

A box contains 12 balls out of which x are black. If one ball is drawn at random from the box, what is the probability that it will be a black ball? If 6 more black balls are put in the box, the probability of drawing a black ball is now double of what it was before. Find x.

Answer 1

Answer:

3

Step-by-step explanation:

Total number of balls = 12

Total number of black balls = x

$\sf{}P (getting\ a\ black\ ball) =\dfrac{x}{12}$

If 6 more black balls are put in the box, then

Total number of balls = 12 + 6 = 18

Total number of black balls = x + 6

$\sf{}P (getting\ a\ black\ ball\ now) =\dfrac{x+6}{18}$

ATQ

$\sf{}2\bigg\lgroup\dfrac{x}{12}\bigg\rgroup=\dfrac{x+6}{18}$

$\sf{}3x=x+6$

$\sf{}2x=6$

$\sf{}x=3$