swerve wrote:There are 5 fictions and 6 non-fictions. How many cases are there such that 2 fictions and 2 non-fictions are selected from there?

A. 90
B. 120
C. 150
D. 180
E. 200

The OA is C.

Please, can any expert explain this PS question for me? I need your help, I don't understand why that is the correct answer. Thanks.

Since this is a case of selection, we will apply Combination.

The number of ways 2 fictions can be selected = 5C2 = 5.4/1.2 = 10;
The number of ways 2 nonfictions can be selected = 6C2 = 6.5/1.2 = 15

The total number of ways 2 fictions and 2 nonfictions are selected = 10*15 = 150 ways.

The correct answer: C

Hope this helps!

-Jay
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swerve wrote:There are 5 fictions and 6 non-fictions. How many cases are there such that 2 fictions and 2 non-fictions are selected from there?

A. 90
B. 120
C. 150
D. 180
E. 200

The OA is C.

Please, can any expert explain this PS question for me? I need your help, I don't understand why that is the correct answer. Thanks.

The number of ways to select two fiction books is:

5C2 = (5 x 4)/2! = 10

The number of ways to select 2 non-fiction books is:

6C2 = (6 x 5)/2! = 15

Thus, the total number of selections is 10 x 15 = 150.

Answer: C