Question

A bag contains 20 balls outof which x balls are red.() If one ball is drawn at random from the bag, find the probability that it is not red.(ü) If 4 more red bails are put into the bag, the probability of drawing a red ball will be 5/4 times the probability of drawing a red ball in the first case.Find the value of x

Answer 1

Total No . of Obs = 20
No . of Red Balls = x
Probability of Red Ball = Favourable Obs / Total No. of Obs
P(of Red Ball) = x/20
Two Red Balls Are Added
So,
No . of Red Balls = x + 4
Total no .of Balls = 20 + 4 = 24
P(of red Ball) = x + 4 / 24
P given 9 times of P obtained in A
5/4 * x/20 = (x + 4)/24
5x / 80 = (x + 4)/24
(x / 16) * 24 = x + 4
3x / 2 = x + 4
3x = 2x + 8
3x - 2x = 8
x = 8
Therefore,
Initial No. Of Red Balls = 8


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