Question

A bag contains 12 balls and some of them are red. If 6 more red balls are put in the bag and is drawn at random the probability doubles than when before. Find the number of red balls in the bag

Answer 1

Number of balls in the bag= 12
Let the number of balls be red=X
Probability of getting a red ball =x/12
If 6 more red balls are added ,
then , total number of balls =18
Now the probability of getting a red ball is
=x+6/18
It is given ,
x+6/18 = 2x/12
12x+72=36x
24x=72
x=3