Percentage changes

Percentage changes

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Overview
Using this Resource
Connecting to the Curriculum
Marking Student Responses
Working with Students
Further Resources
This task is about finding percentages of amounts.

Question 1Change answer

a)  Matu and Shania bought a house-boat for $170 000.
     They redecorated and sold it a year later for 20% more than they paid. 
     What price did they sell their house-boat for? $ 

Question 1Change answer

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b)  Lianna bought a car for $3000 that needed some repairs.
     She did the work herself and sold it for $3900. 
     What percentage had the price of the car increased by? %

Question 1Change answer

 
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c)  A lounge suite was originally priced at $2995.
     Vincent got a 15% discount off this price in a sale. 
     What was the sale price he paid? $ 
Task administration: 
This task can be completed with pencil and paper or online (with auto marking displayed to students).
Level:
5
Curriculum info: 
Maths, Number and Algebra, Number Strategies
Keywords: 
percentages, discount, money
Description of task: 
Students increase and decrease quantities by given percentages.
Learning Progression Frameworks
This resource can provide evidence of learning associated with
Multiplicative thinking, sets 8-9
within the Mathematics Learning Progressions Frameworks.
Read more about the Learning Progressions Frameworks.
Answers/responses: 
 

Y10 (11/1999)
a) 204,000 moderate
b) 30 difficult
c) 2545.75 difficult
Diagnostic and formative information: 
  Common error Likely calculation Likely reason
a)
c)		 34 000
449.25		 170 000 × .2
2999 × .15		 Calculates amount of increase or decrease in price rather than final cost.
a) 85 000
178 500		 170 000 ÷ 2
170 000 × 1.05		 Interprets 20% increase as "divide by 2".
Interprets 20% as .05.
b) 1.3
76.9 or 77		 3900 ÷ 3000
3000 ÷ 3900		 Calculates the proportion it is increased by.
Calculates percentage of final cost.