Åk 6–9
 
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4.2 Decrease

During a sale, the price of bicycles is reduced by 25 %.
The original price for a cycle was 4,000 kr. How much will it cost after the rebate is deducted?

There are two different methods you can use to figure out the answer:

Method 1
25 % of 4,000 kr = ¼ of 4,000 kr

25 % of 4,000 kr = 0.25 · 4,000 = 1,000 kr.

4,000 - 1,000 = 3,000 kr

Answer: The cycle will cost 3,000 kr.


Method 2
Because the price becomes 25 % cheaper, the new price is
100 % - 25 % = 75 % of the original price. If you convert 75 % to a decimal it becomes 0.75.

The new price can then be calculated like this:

0.75 · 4,000 kr = 3,000 kr



This is another example of a rate of change and more about this will be included in chapter 4.3.




Foto: Ryan Savio A


Percentual decrease
If we calculate a decrease in percent the same methods apply as in section 3.1.

We said:



Ex: A digital camera costs 2,500 kr. The camera’s price is then decreased by 500 kr.  By how many percent has the camera’s price decreased?

The part in this case is the change of the price, and the whole is the original price (the old price).

We then get:

Percentage: 500 kr/2,500 kr = 0.2 = 20 %

Answer: The digital camera’s price is decrease by 20 %.