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?
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.
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Solution: Total number of outcomes = 12
P(x) = x/12
When 6 more black balls are put in the box, total number of balls = 12 + 6 = 18
Number of black balls = 6 + x
P(black) = (x+6)/18
As per question;
(x+6)/18 = 2*x/12
or, x+6 = 3x
or, 2x = 6
or, x = 3
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