A bag 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.

Asked by Aavi Loyal | 31st Dec, 2013, 03:50: PM

Expert Answer:

There are 12 balls in total.
 
Let the number of black balls be x.
 
Thus the probability of getting a black ball
Now if we add 6 more black balls, the total number of balls = 12 +  6 = 18
 
The probability of getting a black ball after adding 6 more balls =
Given that the new probability is twice the old one.
 
Therefore,
 

Answered by Vimala Ramamurthy | 31st Dec, 2013, 06:41: PM

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