# a bag contains 15 balls of which x are blue and remaining are red. if the number of red balls are increased by 5,the probability of red ball doubles.find x

In First Case,

No Of Balls = 15
No Of Blue Balls = x
No Of Red Balls = 15 - x
Probability of taking a red ball is; P(E) = 15 - x
15

After 5 red balls are added,
No of balls = 15 + 5 = 20
No of blue balls = x
No of Red Balls = (15 - x) + 5 = 20 - x
Probability of taking a red ball is; P(E) = 20 - x
20

According to your question, 15 - x    x  2   =  20 - x
15                       20

30 - 2x   =  20 - x
15                20

600 - 40 x = 300 - 15 x
​                                                          300 =25 x
x = 12

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