Percentage Increase and Decrease

[Pages:2]Percentage Increase and Decrease

An increase is when the price of an item or quantity goes up and a decrease is when it is reduced or goes down.

Percentage difference

To calculate the percentage increase or decrease in the price or quantity you need to find the percentage that it is being increased or decreased by. Having found this percentage you need to add this onto the original price or quantity if it is being increased or take it off if it is being decreased.

You can find a percentage in a number of different ways. Here are some examples:

A dress costing ?20 is being increased by 15% Multiply the price by the percentage and the divide this by 100 Calculation: 20 x 15 ? 100 20 x 15 = 300, 300 ? 100 = 3 The price of the dress is being increase by ?3 so this is added to ?20 to give a new price of ?23

A pair of trainers in a sale are priced at ?40 less a 30% reduction (decrease) Multiply the price by the percentage and the divide this by 100 Calculation: 40 x 30 ? 100 40 x 30 = 1200, 1200 ? 100 = 12 The price of the trainers are being reduced by ?12 so the sale price would be ?40 - ?12 = ?28

Calculating percentage increase/decrease using multipliers

Using multipliers to calculate percentage increase or decrease is a one-step process where the calculation gives an answer with the percentage increase or decrease already added on or taken off. To calculate a percentage increase or decrease you need to multiply the price or quantity by the decimal equivalent of the percentage. If something is being increased add the percentage to 100 and then divide this by 100 to find the multiplier. If an item is being decrease subtract the percentage from 100 and the divide by 100.

Here are some examples:

The price of a computer costing ?250 is being increased by 12% Multiply the price by the multiplier (100 +12 ? 100 = 1.12) 250 x 1.12 = 280. The new selling price will be ?280

The price of a pair of trousers costing ?35 is being decreased by 25% in a sale Multiply the price by the multiplier (100 -25 ? 100 = 0.75) 35 x 0.75 = 26.25. The new selling price will be ?26.25

Now try these: 1. A pair of shoes cost ?42. You have a voucher that gives you a 15% discount off the selling price. What price will you pay for the shoes?

2. A new car costs ?12000 in a showroom. The company has a sales promotion and offers a 20% discount on new car sales. What would be the sale price for the car?

3. You are re-decorating your bedroom and need to buy 20m2 of carpet. The carpet shop is giving 25% extra on carpet sales. How much carpet will you get?

4. You borrow ?2000 from your bank to buy some furniture for your home. The bank charges 10% interest on the loan. How much would you pay back to the bank for your loan including the amount you borrowed?

5. A Garden Centre is having a sale and has reduced prices on certain items. Calculate the new prices. Shrubs ? 25% off were ?20 now . . . . . . . . . Planters ? 10% off were ?15 now . . . . . . . . . Compost ? 20% off were 20% now . . . . . . . . .

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