Percent Increase or Decrease Shortcuts

Lesson 2: Pricing - Percent Increase or Decrease Shortcuts

   Constructing Knowledge

When calculating percent increases or decreases, there is another method to find the final amount.

You can first calculate the final price in terms of an overall percentage, then apply the percentage to the original amount.

For a price increase (such as GST):

You will pay 100 % for the item plus 5% for the GST.

final percentage	= 100% + 5%
	= 105%

This means, in total, you will pay 105% of the original price of the item.

For a price decrease (such as a sale):

You will pay 100% for the item less the sale percent

final percentage	= 100% - 25%
	= 75%

This means you will pay 75% of the original price of the item.

Below are the examples from the previous section with the shortcut solutions.

   Multimedia

A video describing a shortcut for calculating cost after a percentage increase or percentage decrease is provided.

EXAMPLE 1

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The GAP sells socks for $2.50 per pair. Calculate the final cost of the pair of socks and determine the final cost of the socks.

Solution

Adding GST to the original price of an item means the final cost will be 105% (100% + 5%) of the original price.

final cost	= $2.50 × 105%
	= $2.50 × 1.05
	= $2.63

The final cost of the socks will be $2.63

EXAMPLE 2

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Harley's Hair shop is having a 25% off sale on hair coloring. She normally charges $90.00 for a single color. What is the sale price for this service?

Solution

Subtracting 25% from the original price of the service means the final cost will be 75% (100% − 25%) of the original price.

sale price	= $90.00 × 75%
	= $90.00 × 0.75
	= $67.50

The sale price for a single color is $67.50

You may choose to use these shortcut methods in your solutions, but it is not a requirement.

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