Probability Practice Test 1

Question : 13 of 40

Marks: +1, -0

There are 4 white and 4 black balls in a bag and 3 balls are drawn at random. If balls of same colour are identical, the probability that none of them is black, is

$1/4$
$1/14$
$1/2$
None of these

Validate

Solution:

There are 4 identical white and 4 identical black balls and we have to select 3, which can be selected in the following pattern:

white	3	2	1	-
black	-	1	2	3

i.e., in all 4 ways.It should be noted that the ways of selecting 3 white balls from 4 white balls is not equal to

^4C_3

since the white balls are identical, it is equal to 1. Similar is the cases for 2, 1, etc.
Now the number of ways of selecting 3 white balls = 1.
Hence, required probability

= 1/4

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