Unit 4
6 marks · NormalA garden centre increases the price of a decorative plant by 6% each year. Meanwhile, the area of land for these plants is calculated using a formula.
The plant originally costs $15. The land forms a rectangle with length 8 m and width 5 m.
Calculate the price of the plant after 3 years. Give your answer correct to 2 decimal places.
Write an algebraic expression for the area A of the rectangular land in terms of its length l and width w.
Calculate the area of the land using the formula you wrote in (b).
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) $17.87 $
(b) A = l × w
(c) 40 m^2
Common mistakes: Confusing simple and compound interest; Using l + w instead of l × w
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Identifies compound interest method using multiplying factor 1.06^n.
A1 (a) · 2 marks · Correct calculation of final amount, rounded to 2 decimal places. (follow-through)
B1 (b) · 1 mark · Correct area formula A = l × w or A = lw.
M2 (c) · 1 mark · Substitutes values into area formula.
A2 (c) · 1 mark · Accurate calculation to obtain 40 m^2. (follow-through)
Worked solution
(a) Original price = $15
Rounded: $17.87
(b) Area formula: A = l × w
(c) Substituting l = 8 m and w = 5 m: