SPM 2023 Add Maths Paper 2, Question 14Linear Programming

Solved on video in English and Bahasa Melayu · Form 5, Linear Programming · 5:02 video

The question

(a)

Julie produces two types of dolls, Mal and Tod. Table 3 shows: Mal — x units at RM16.80 per unit; Tod — y units at RM14.00 per unit. The dolls satisfy the following constraints: I: the total number of Mal and Tod dolls is less than p units; II: the number of Tod dolls is more than q units; III: the number of Tod dolls is not more than 2 times the number of Mal dolls.

(a) Constraints I and II are shown on the provided graph; the shaded region represents the points satisfying both. State the value of p and of q.

(b)

Constraint III: the number of Tod dolls is not more than 2 times the number of Mal dolls; p = 16, q = 4.

(b) Write an inequality for constraint III, other than x ≥ 0 and y ≥ 0. Hence, construct and label the region R which satisfies all the constraints.

(c)(i)

Use the region R constructed in (b).

(c)(i) On a particular day, the ratio of the number of Tod dolls to the number of Mal dolls produced is 3 : 2. Determine the possible numbers of Mal dolls produced on that day.

(c)(ii)

Mal costs RM16.80 per unit and Tod costs RM14.00 per unit; region R is as in (b).

(c)(ii) Given that the total cost to produce the Mal dolls and Tod dolls is RMk, express k in terms of x and y. Hence, draw the objective function and find the maximum cost.

SPM 2023 Add Maths Paper 2, Question 14: the question as drawn in Eduly's video5:02

Part (a)

Step 1

Constraint I: x + y < p. From the graph the boundary line x + y = p has intercepts at 16, so p = 16.

Why this step

Turn the inequality into its boundary line x + y = p. Where that line meets an axis, x or y is 0, so the intercept equals p.

1 more step, with the reason for it, in the full solution

Final answer

p = 16, q = 4

Where students lose marks

Watch out: read both values. p comes from x + y = 16, and q from the horizontal line y = 4.

Part (b)

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

Final answer

y ≤ 2x; region R constructed (see video)

Where students lose marks

Watch out: R lies below y = 2x, above y = 4 and below x + y = 16. Check each side.

Part (c)(i)

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

Final answer

Mal = 4 or 6

Where students lose marks

Watch out: keep only whole-number points on y = (3/2)x inside R, or you will miss or add invalid x values.

Part (c)(ii)

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

Final answer

k = 16.80x + 14.00y; maximum cost = RM238 at (10, 5)

Where students lose marks

Watch out: after k = 16.8x + 14y, draw the objective line and slide it to the last point of R, (10, 5).

Watch every step of this question solved on video (5:02), 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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