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Calculating Percentage Changes

Achievement Objectives:

Achievement Objective: NA5-3: Understand operations on fractions, decimals, percentages, and integers.
AO elaboration and other teaching resources

Specific Learning Outcomes: 

Estimate and find percentages of whole number and decimal amounts.

Description of mathematics: 

Number Framework Stage 8

Required Resource Materials: 
Calculating percentage changes (Material Master 8-18).







The need to calculate percentages is often not obvious to students. It really is a

method of comparing fractions by giving both fractions a common denominator,

namely hundredths. So it is useful way to view percentages as hundredths.

Using Number Properties

Problem: “Tom’s Toothbrush Company makes a profit of $57,892.12 on sales of

$456,789.23. A much bigger company United Industries makes a profit of

$453,884.01 on sales of $4,489,000.89.

Turn the fraction profit of each company into a percentage to see which company

makes a better profit. Round the answers sensibly.”

(Answer: Tom’s fractional profit is 57892.12/456789.23 = 0.126737051 0.127 =  12.7%. United Industries’ fractional profit is 453884.01/4489000.89 = 0.101110251  0.101 = 10.1%. So Tom’s company makes a slightly better profit.)

Examples: Worksheet (Material Master 8–18).

Understanding Number Properties:

Make up two fractions that are close to each

other and use percentages to show which fraction is larger.