Everything Maths Grade 10

P(A) =

n(A)

n(S)

=

5

36

P(B) =

n(B)

n(S)

=

11

36

P(A\B) =

n(A\B)

n(S)

=

2

36

P(A[B) =

n(A[B)

n(S)

=

14

36

Step 2: Write down and check the identity

P(A[B) =P(A) +P(B)P(A\B)

RHS=

14

36

LHS=

5

36

+

11

36

2

36

=

5

36

+

9

36

=

14

36

)RHS=LHS

Exercise 14 – 5:

1.A group of learners is given the following event sets:

Event SetA 1 2 5 6 Event SetB 3 Event SetA\B empty

The sample space can be described asfn:n εZ; 1 n 6 g.

They are asked to calculate the value ofP(A[B). They get stuck, and you offer to calculate it for them.

Give your answer as a decimal number, rounded to two decimal places.

2.A group of learners is given the following event sets:

Event SetA 1 2 6 Event SetB 1 5 Event SetA[B 1 2 5 6

The sample space can be described asfn:n εZ; 1 n 6 g.

They are asked to calculate the value ofP(A\B). They get stuck, and you offer to calculate it for them.

Give your answer as a decimal number, rounded to two decimal value.

For more exercises, visit http://www.everythingmaths.co.za and click on ’Practise Maths’. 1.2GWP 2.2GWQ

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484 14.5. Probability identities