00:01
In this problem, it is said that a computer lab has 20 computers and a virus infected 8 of these computers.
00:07
Now 10 computers are selected at random and we need to find the probability that exactly 6 of them are infected by the virus.
00:15
So the required probability will be the number of favorable outcomes divided by the total number of outcomes.
00:21
First of all, consider the total number of outcomes.
00:23
There are a total of 20 computers and out of them 10 are selected at random.
00:27
This can be done in 20c10 ways.
00:30
Here we use c which represents combination and we use combination and not permutation in this case because the order of selection of the computers does not matter.
00:39
Next, consider the number of favorable outcomes.
00:41
That will be the number of ways 10 computers are selected so that exactly 6 are infected by the virus.
00:46
So out of the 8 computers which have been infected, 6 are selected in 8c6 ways...