Comparing prices and calculating a new price after a discount or increase is an important skill.
In a store, it is easy to compare prices using the unit price of a product. For example, the unit price can be stated as per litre (milk costs 0,69 € / l) or per kilogram (the price per kilo of candy is 7,50 € / kg).
Example 1. A 250 g bag of Lakupala costs 1,80 € and a bag of 120 g of Choco costs 1,95 €. Calculate the prices per kilo of each candy.
Calculating a changed value
Percentage factors are often used to calculate a changed value (for example, a new price).
If the price increases by 5%, the percentage factor is 100% + 5% = 105%, from which the calculation is a decimal number of 1,05.
If the price of the product decreases by 5%, the percentage factor is 100% - 5% = 95%, from which 0,95 is used for the calculation.
Example 2. The price of a product in March was 16,90 €. The price was raised by 7% in April. Calculate the new price.
Example 3. Calculate the discount price of a product when it originally cost 27,80 € and the discount is 5%.
Often, a situation arises in the calculation of percentages, where it is necessary to determine a change as a percentage. Such a situation is, for example, the calculation of a discount rate.
The problem can be solved by calculating how much of the new value is from the original value and interpreting the resulting decimal number as a percentage.
Example 4. The original price of a product was 199,90 € and it was sold at a discount price of 89,95 €. Calculate the discount percentage.
45% of the price of the product remains, which means that the discount percentage is 55%.
Example 5. A salary increased from 2010 € to 2090 €. Calculate by what percent the salary was raised.
The salary change in a percentage factor is 1,04. This corresponds to a percentage of 104% and the salary increase was 4%.
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1. The price of a product is increased by 6,5%. By what percentage factor should the price be multiplied in order to obtain an increase in price?
2. The price is reduced by 12%. What percentage factor should be used to multiply the price to get a discounted price?
3. A television costs 549 €. You get a 37% discount. Calculate the discount price of the TV.
4. The price of a jacket was 45,90 € and was increased by 8%. Calculate the new price of the jacket.
5. Mini plum tomatoes are sold in 250 g boxes. A box costs 2,19 €. Calculate the price per kilogram of tomatoes.
6. Sima is sold in 0,75 litre bottles. A bottle costs 5,85 €. Calculate the price per litre.
7. A price of 92 € is increased first by 5% and then again by 12%. Calculate the final price.
8. Calling an electricity company's service number costs 8,35 cents / call + 16,69 cents / min. How much does a 5 minute call cost?
9. The electricity company offers an electricity contract where the basic fee is 2,90 € and 5,99 cents / kWh.
Calculate how much electricity you have to pay when 2000 kWh of electricity are consumed per year.
10. Jam is sold in a 400 g jar that costs 1,99 €. The berry content of the jam is 40 g / 100 g. Calculate the price per kilogram of berries in jam.