MRSM Trial 2025 Add Maths Paper 2, Question 13Linear Programming
Solved on video in English · Form 5, Linear Programming · 6:20 video
The question
Roy's Collection is a clothing boutique that accepts orders for trousers and shirts. Table 2 shows the preparation and sewing time per item — Trousers: preparation 45 min, sewing 50 min; Shirt: preparation 30 min, sewing 70 min. The maximum preparation time is A hours and the sewing time is at least 5 hours 50 minutes. In a certain period the boutique prepares x trousers and y shirts, and the ratio of trousers to shirts successfully prepared does not exceed 4 : 5.
(a) The inequality involving the maximum preparation time A hours is represented by the straight line given on the graph paper. Find the value of A.
Roy's Collection (trousers: prep 45 min, sewing 50 min; shirt: prep 30 min, sewing 70 min; max preparation A = 10 hours; sewing at least 5 h 50 min; ratio trousers : shirts does not exceed 4 : 5; x trousers, y shirts).
(b) Write two inequalities other than the inequality in (a), x ≥ 0 and y ≥ 0, that satisfy all of the above constraints.
Roy's Collection, with constraints 45x + 30y ≤ 600, 50x + 70y ≥ 350, x/y ≤ 4/5, x ≥ 0, y ≥ 0.
(c) Construct and label the region R which satisfies all constraints.
Roy's Collection, region R as constructed. The price of a pair of trousers and a shirt is RM350 and RM200 respectively.
(d) It is given that the boutique successfully prepared x pairs of trousers and y shirts within 2 days. By using the objective function, determine whether the boutique is able to continue its operation if the monthly cost is RM40 000.
6:20Part (a)
Step 1
The preparation-time constraint is 45x + 30y ≤ A × 60 (A hours in minutes). At x = 0 the boundary line gives 30y = 60A → y-intercept = 2A.
Why this step
The table times are in minutes but A is in hours, so we use A × 60. Forgetting this conversion is a common way to lose the mark.
1 more step, with the reason for it, in the full solution
Final answer
A = 10
Where students lose marks
Watch out: A is in hours but the table is in minutes, so use 60A, and read the y-intercept carefully from the graph.
Part (b)
2 more steps, each with the reason for it, in the full solution
Final answer
50x + 70y ≥ 350 and x/y ≤ 4/5
Where students lose marks
Watch out: 5 h 50 min is 350 minutes, not 550, and 'does not exceed 4 : 5' means x/y ≤ 4/5, not ≥.
Part (c)
2 more steps, each with the reason for it, in the full solution
Final answer
Region R shaded and labelled (see video)
Where students lose marks
Watch out: test each line to shade the correct side, and remember to label the region R.
Part (d)
4 more steps, each with the reason for it, in the full solution
Final answer
Yes, RM64 500 > RM40 000
Where students lose marks
Watch out: RM4300 is only for 2 days. Multiply by 15 before comparing with RM40 000, and test only points inside R.
Watch every step of this question solved on video (6:20), with the reason behind each step and a box that checks your own answer.
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