1.1. Independent Events http://www.ck12.org
4 suits 3 face cards per suit
↘ ↙
Therefore, the total number of face cards in the deck= 4 × 3 = 12P(A) =
12
52
P(B) =
11
51
P(A AND B) =
12
52
×
11
51
orP(A∩B) =12
52
×
11
51
=
33
663
P(A∩B) =
11
221
Example 3:You have different pairs of gloves of the following colors: blue, brown, red, white and black. Each
pair is folded together in matching pairs and put away in your closet. You reach into the closet and choose a pair of
gloves. The first pair you pull out is blue. You replace this pair and choose another pair. What is the probability that
you will choose the blue pair of gloves twice?
Solution:
P(blue and blue) =P(blue∩blue) =P(blue)×P(blue)=1
5
×
1
5
=
1
25
What if you were to choose a blue pair of glovesora red pair of gloves? How would this change the probability?
The wordORchanges our view of probability. We have, up until now worked with the wordAND. Going back to
our VENN DIAGRAM, we can see that the sample space increases forAorB.