Kuala Lumpur Trial 2025 Add Maths Paper 2, Question 12Linear Programming
Solved on video in English · Form 5, Linear Programming · 6:53 video
The question
Puan Anisah produces two types of products, chocolate cakes and potato bread. Each product requires two ingredients, wheat flour and sugar. The ingredients needed to make one chocolate cake and one potato bread are shown in Table 2: a chocolate cake needs 300 g wheat flour and 100 g sugar; a potato bread needs 150 g wheat flour and 200 g sugar. She has 12 kg of wheat flour and 7 kg of sugar. The number of chocolate cakes produced is more than two-thirds the number of potato breads. She produces x chocolate cakes and y potato breads.
(a) Write three inequalities, other than x ≥ 0 and y ≥ 0, which satisfy all the above constraints.
Puan Anisah produces x chocolate cakes and y potato breads subject to the constraints in part (a).
(b) Using a scale of 2 cm to 10 units on both axes, construct and shade the region R which satisfies all the above constraints.
Puan Anisah produces x chocolate cakes and y potato breads subject to the constraints in part (a), with region R drawn in part (b).
(c) Based on the graph obtained in (b), find: (i) the maximum number of potato bread that can be produced if the shop produces 20 chocolate cakes.
(c)(ii) the maximum profit obtained by Puan Anisah if the profit from selling a chocolate cake and a potato bread are RM20 and RM25 respectively.
6:53Part (a)
Step 1
Wheat flour constraint (12 kg = 12 000 g): 300x + 150y ≤ 12 000; divide by 150 → 2x + y ≤ 80.
Why this step
The table is in grams, so change 12 kg to 12 000 g first. It's ≤ because she can't use more flour than she has.
2 more steps, each with the reason for it, in the full solution
Final answer
2x + y ≤ 80, x + 2y ≤ 70, x > (2/3)y
Where students lose marks
Watch out: convert kg to g first, use ≤ for the resource limits, and write the strict x > (2/3)y for 'more than'.
Part (b)
4 more steps, each with the reason for it, in the full solution
Final answer
Region R shaded (see video)
Where students lose marks
Watch out: x = (2/3)y is dashed (strict >). Check the side you shade, and use the scale 2 cm to 10 units.
Part (c)(i)
4 more steps, each with the reason for it, in the full solution
Final answer
Maximum potato bread = 25
Where students lose marks
Watch out: use the sugar line (y ≤ 25), not the flour line (y ≤ 40), because it is the tighter limit.
Part (c)(ii)
4 more steps, each with the reason for it, in the full solution
Final answer
Maximum profit = RM1100 at (30, 20)
Where students lose marks
Watch out: compare all corners of R, not just one, and match RM20 to cakes (x) and RM25 to breads (y).
Watch every step of this question solved on video (6:53), with the reason behind each step and a box that checks your own answer.
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