SPM 2019 Add Maths Paper 1, Question 20Probability Distribution

Solved on video in English and Bahasa Melayu · 2 marks · Form 5, Probability Distribution · 4:59 video

The question

The events A, B and C are independent but not mutually exclusive. It is given that P(A) = x, P(B) = y and P(C) = z. Express in terms of x and/or y and/or z: (a) P(A∩B∩C), (b) P(A∪B).

[2 marks]

SPM 2019 Add Maths Paper 1, Question 20: the question as drawn in Eduly's video4:59

Step 1

Since A, B, C are independent, P(A∩B∩C) = P(A) x P(B) x P(C) = xyz.

Why this step

Independent means one event doesn't change the chances of the others, so 'all three happen' is just the three chances multiplied together.

3 more steps, each with the reason for it, in the full solution

Final answer

(a) xyz, (b) x + y − xy

Where students lose marks

Watch out: A and B are not mutually exclusive, so P(A∪B) is not x + y. Subtract the overlap P(A∩B) once.

Watch every step of this question solved on video (4:59), with the reason behind each step and a box that checks your own answer.

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