Selangor Trial 2025 Add Maths Paper 1, Question 12
Solved on video in English · 5:06 video
The question
In a survey carried out in a school, it was found that 1 out of 3 students have mobile phones. If 8 students are chosen at random, (a) state all the possible outcomes.
If 8 students are chosen at random, (b) calculate the probability that more than 2 students have mobile phones.
5:06Part (a)
Step 1
Let X be the number of the 8 chosen students who have a mobile phone. X follows a binomial distribution with n = 8.
2 more steps, each with the reason for it, in the full solution
Final answer
X = {0, 1, 2, 3, 4, 5, 6, 7, 8}
Where students lose marks
Watch out: 0 is a valid outcome, so the list starts at 0 and ends at 8. List values of X, not probabilities.
Part (b)
6 more steps, each with the reason for it, in the full solution
Final answer
P(X > 2) = 0.5318
Where students lose marks
Watch out: 'more than 2' means X > 2, not X ≥ 2. Use p = 1/3 (has a phone) and subtract from 1.
Watch every step of this question solved on video (5:06), with the reason behind each step and a box that checks your own answer.
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