# 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? - Mathematics

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.

#### Solution

Total number of balls = 12

Total number of black balls = x

P (getting a black ball)  =  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

P (getting a black ball now)  = (x+6)/18

According to the condition given in the question,

2(x/12) - (x+6)/18

3x = x+6

2x = 6

x = 3

Concept: Probability - A Theoretical Approach
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#### APPEARS IN

NCERT Class 10 Maths
Chapter 15 Probability
Exercise 15.2 | Q 4 | Page 311