Question

A bag contains 40 balls out of which some are blue and remaining are black. If one ball is picked up
randomly then probability of drawing a red ball is 11/20 and that of blue ball is 1/5 .Find the number of
black balls in that bag. Justify your answer.​

Answer 1

Answer:

Let no. of red balls = x, no. of blue balls =y and no.of black balls = z.

Probability of drawing a red ball = P (red ball) =  

20

11

​  

=  

40

x

​  

 

⇒ x=22

Probability of drawing a blue ball = P (Blue ball) =  

5

1

​  

=  

40

y

​  

 

⇒ y=8

∴ No of black balls = 40- 22 -8 =10

COLCLUSION:

ANSWER = 10