Download Lesson 5: Mutually Exclusive Events

Starter
A school has 564 students. 229 of them were absent
for at least one day during Term due to sickness, and
111 students missed some school because of family
holidays. 296 students attended every day of Term.
What is the probability a student:
 Were absent during Term for any reason
 Missed school for both illness and holidays
 Were away for holidays but not sickness
268/
56
4 72/564
39/
564
Note 6: Complementary Events
If A is an event, then not A is the
complementary event, written A′.
Example: The probability a person passes Statistics
is 0.6. What is the probability a person doesn’t pass
Statistics ?
P(doesn’t pass Stats) = 1 – 0.6 = 0.4
Note 7: Mutually Exclusive Events
Mutually exclusive events cannot both
occur. They have nothing in common.
ie. No intersection.
P(A U B) = P(A) + P(B)
Example: In a pack of 52 cards, what is the probability
that a card is chosen at random will be a heart or a club?
P(heart or club)
= P(heart) + P(club)
=¼+¼=½
Page 161
Exercise D