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:

let y be the probability

y=x/12

12y=x --(1)

12y=x (*3)

now prob doubles

2y=x+6/18

36y=x+6 --(2)

sub 1 from 2

  36y=x+6

-  12y=x

24y=6

y=1/4

putting in 1

12 *1/4 =x

3=x

Solved !!!

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Answer 2

Answer:

x= 3

solution :

Total number of balls =12

Total number of black balls be x

Therefore, P(getting a black ball ) = x/12

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

Total number of balls = 12 +6 = 18

Total number of black balls = x +6 P ( getting a black ball ) = x+6/18

ATQ :-

2× x /12 = x+6 /18

=> 18 x = 6 ( x+6 )

=> 18 x = 6x + 36

=> 12 x = 36

=> 36/12 = 3.

Therefore , x = 3

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