Complement — Grade 7 Accelerated, what it means and where it is taught
Everything except the event. P(not A) = 1 - P(A).
Taught in Grade 7 Accelerated.
Where it is taught
Practise this idea
3 questions in the course bank use Complement, in Probability of Simple Events, Probability of Compound Events, Geometric Construction.
Problem 1
Three fair coins are flipped. Find P(at least one head).
Worked answer
7/8
The opposite is no heads at all: TTT
There are 23 = 8 equally likely outcomes, so P(TTT) = 18
1 - 18 = 78
Problem 2
Two fair dice are rolled. Find P(at least one 6).
Worked answer
11/36
P(no six on one die) = 56
P(no six at all) = 56 × 56 = 2536
1 - 2536 = 1136
Problem 3
Find the complement of 35°.
Worked answer
55
90 - 35 = 55°