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 now is double of what it was before. Find x.

number of black balls = x

∴ number of favorable outcomes = x

total number of balls = 12

∴ total number of outcomes = 12

∴  P (black ball) =

now 6 new black balls added 

∴ number of black balls = x + 6

∴ number of favorable outcomes = x + 6

total number of balls = 12 + 6 = 18

∴  P (black ball) =

according to the question

=

=

6 (x + 6) = 18x

6x + 36 = 18x

36 = 18x - 6x

36 = 12x

3 = x

  • 52

x/12

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

x+6/18=x/6

6x+36=18x

12x=36

x=3

the black balls are 3

hope this helps u

  • 16

thanks bro !!

  • -6
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