SPM 2018 Add Maths Paper 2, Question 15Linear Programming
Solved on video in English and Bahasa Melayu · 10 marks · Form 5, Linear Programming · 6:34 video
The question
Use the graph paper provided on page 23 to answer this question. Detach the graph paper and tie it together with your answer booklet. A department store sells two types of perfumes, P and Q. The selling price of perfume P is RM400 per bottle and perfume Q is RM100 per bottle. A promoter, Zie sells x bottles of perfume P and y bottles of perfume Q. She will be given a 5% commission of her total sales if she is able to achieve the following targets: I. The total number of bottles of perfume sold is at least 50. II. The minimum total sale is RM8 000. (a) Write two inequalities, other than x >= 0 and y >= 0, which satisfy all the above constraints. (b) Use a scale of 2 cm to 10 bottles on both axes, construct and shade the region R which satisfies all the above constraints. (c) Use the graph constructed in 15(b) to answer the following questions: (i) Find the minimum number of bottles of perfume P and perfume Q to be sold if the number of bottles of perfume Q sold is twice the number of bottles of perfume P. (ii) Determine the minimum amount of commission received by Zie if she is able to sell 35 bottles of perfume P.
[10 marks]
6:34Step 1
Constraint I ('at least 50 bottles in total'): x + y >= 50. Constraint II ('total sale at least RM8 000', where sale = 400x + 100y): 400x + 100y >= 8000, which simplifies (dividing every term by 100) to 4x + y >= 80.
Why this step
'At least' and 'minimum' both mean ≥, never ≤. Dividing by 100 keeps the numbers small, so the line is easier to plot.
6 more steps, each with the reason for it, in the full solution
Final answer
(a) x + y ≥ 50, 4x + y ≥ 80; (b) Region R (see video); (c)(i) 17 of P, 34 of Q; (c)(ii) RM775
Where students lose marks
Watch out: the question asks for the 5% commission, not the total sales. Give RM775, not RM15 500.
Watch every step of this question solved on video (6:34), with the reason behind each step and a box that checks your own answer.
No card. Every past-year question on video, in English and BM.
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