SPM 2024 Add Maths Paper 2, Question 6Probability Distribution

Solved on video in English and Bahasa Melayu · Form 5, Probability Distribution · 6:53 video

The question

Table 1 shows the categories for body mass index of a group of male workers in a company. The body mass index is normally distributed.

Body mass index | Category x < 18.5 | Underweight 18.5 ≤ x < 25 | Normal weight 25 ≤ x < 30 | Overweight x ≥ 30 | Obese

It is given that 44% of the workers are categorised as either underweight or normal weight while 12% were categorised as obese. It is found that 1 out of n workers were in the underweight category.

Find the value of n.

Step 1

Set up two equations using the standard normal distribution Z = (X − μ)/σ.

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

Final answer

n = 33

Where students lose marks

Watch out: z is negative when the area is below 0.5. Keep signs right solving for μ and σ, then set 1/n = P(underweight).

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