SPM 2020 Add Maths Paper 1, Question 22Probability Distribution

Solved on video in English and Bahasa Melayu · 3 marks · Form 5, Probability Distribution · 5:15 video

The question

Diagram 11 shows a plan of a game. The game starts at A and ends at B. Each two intersections is connected by a path. A player moves randomly at every intersection and cannot return using the same path. Find the probability that the player will arrive at B by passing at most three paths.

[3 marks]

SPM 2020 Add Maths Paper 1, Question 22: the question as drawn in Eduly's video5:15

Step 1

List the routes from A to B that use at most three paths (1, 2 or 3 paths) without reusing a path, then count the total number of route outcomes (the sample space).

Why this step

Multiplying choices overcounts, because a route stops at B or when no fresh path is left. So we trace and list the routes one by one.

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

Final answer

2/7

Where students lose marks

Watch out: multiplying the choices at each intersection overcounts. Trace and list the real routes to get the correct sample space.

Watch every step of this question solved on video (5:15), with the reason behind each step and a box that checks your own answer.

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