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4.1.1 Probability (A-level only)

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Question 77

The events AAA and BBB satisfy

P(A)=x,P(B)=y,P(A∪B)=0.72,P(B∣A)=0.2 P(A) = x, \quad P(B) = y, \quad P(A \cup B) = 0.72, \quad P(B|A) = 0.2 P(A)=x,P(B)=y,P(A∪B)=0.72,P(B∣A)=0.2
a.

Show that

4x+5y=3.6 4x + 5y = 3.6 4x+5y=3.6
[3]
b.

The events BBB and CCC are mutually exclusive such that

P(B∪C)=0.9,P(C)=14x+y P(B \cup C) = 0.9, \quad P(C) = \frac{1}{4}x + y P(B∪C)=0.9,P(C)=41​x+y

(i) Find a second equation in xxx and yyy.

(ii) Hence find the value of xxx and the value of yyy.

[5]
c.

Determine whether or not AAA and BBB are statistically independent. You must show your working clearly.

[2]
Markscheme

4.1.1 Probability (A-level only) Questions

  1. A Level
  2. /Maths
  3. /4.1.1 Probability (A-level only)

111 exam-style questions on WJEC A Level Maths 4.1.1 Probability (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.

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