Selangor Trial 2025 Add Maths Paper 2, Question 13Index Numbers

Solved on video in English · Form 4, Index Numbers · 6:53 video

The question

(a)

Table 2 shows information for four ingredients, A, B, C and D, used to produce a chocolate cake. Price index in 2023 based on 2022: A = 110, B = 120, C = 125, D = 150. Change in price index from 2023 to 2024: A increased 25%, B unchanged, C unchanged, D decreased 10%. Weightage: A = m, B = 30, C = 15, D = 15. (a) The price of ingredient A in the year 2024 is RM35. Find the corresponding price in the year 2022.

(b)

(b) The composite index for the four ingredients in the year 2023 based on the year 2022 is 121.25. Calculate the value of m.

(c)

(c) Calculate the production cost of the chocolate cake in the year 2024 if the corresponding cost in the year 2022 is RM80.

Selangor Trial 2025 Add Maths Paper 2, Question 13: the question as drawn in Eduly's video6:53

Part (a)

Step 1

First find the price index of A for 2024 based on 2022. Index(2023/2022) = 110, and A increased 25% from 2023 to 2024 so Index(2024/2023) = 125.

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

Final answer

RM25.45

Where students lose marks

Watch out: don't apply 25% straight to RM35. Chain the indices first, then divide by 137.5 (not multiply) to get the 2022 price.

Part (b)

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

Final answer

m = 40

Where students lose marks

Watch out: m belongs in the denominator too (m + 60), and take care expanding 121.25(m + 60).

Part (c)

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

Final answer

RM104.00

Where students lose marks

Watch out: use D's 2024/2022 index of 135, not 150, and remember A's weight is m = 40 from part (b).

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