Question

13. A bag has 20 white balls, 10 red and 15 black balls
balls. Find the fraction of
(a) Red balls
(b) Black balls
(c) White balls.
​

Answer 1

a) 10/45 = 2/9

b) 15/45 = 1/3

c) 20/45 = 4/9

Answer 2

Answer:

Let A: be the event that first ball is white

And B: be the event that second ball is black

P(A)=

Total number of balls

Number of white balls

=

25

10

=

5

2

P(B)=

Total number of balls left

Number of black balls

=

24

15

=

8

5

{24 because 1 ball was taken out and not replaced}

Hence the probability that first is white and second is black =

5

2

×

8

5

=

4

1