Question

A bag contain 12 balls of which x are red,when 18 more red balls are added,the probability of selecting a red ball is 9/10. Find the number of red balls that were oignally in the bag.

Answer 1

Answer:

Number of balls in bag = 12

number of red balls in bag = x

{when 18 more balls are added}

Total number of balls = 12+18= 30

now number of red balls = x+18

and probability of getting red balls

=9/10

= ( no. of red balls) = 9

( total no. of balls) 10

= (x+18) =9

30 10

(cross multiplication)

10(x+18) = 9×30

10x 180 = 270

10x = 270-180

10x = 90

x = 90/10

x = 9

Total no. of red balls in the original bag = 9 balls