Depreciation (Cambridge (CIE) IGCSE International Maths)
Revision Note
Written by: Jamie Wood
Reviewed by: Dan Finlay
Depreciation
What does depreciation mean?
Depreciation is where an item loses value over time
E.g. cars, mobile phones, etc
Depreciation is usually calculated as a percentage decrease at the end of each year
This works the same as compound interest, but with a percentage decrease
How do I calculate depreciation?
A similar method to compound interest can be used
Change the multiplier to one which represents a percentage decrease
e.g. a decrease of 15% would be a multiplier of 0.85
If a car worth $ 16 000 depreciates by 15% each year for 6 years
Its value will be 16 000 × 0.856, which is $ 6034.39
If you are asked to find the amount the value has depreciated by:
Find the difference between the starting value and the new value
Depreciation formula
An alternate method is to use the following formula to calculate the final balance
Final balance = where
P is the original amount,
r is the % increase
and n is the number of years
Note that all of is the multiplier
e.g. 0.75 for a 25% depreciation
This formula is not given in the exam
Worked Example
Mercy buys a car for £20 000. Each year its value depreciates by 15%.
Find the value of the car after 3 full years.
Identify the multiplier
100% - 15% = 85%
m = 1 - 0.15 = 0.85
Raise to the power of number of years
0.853
Multiply by the starting value
£20 000 × 0.853
£12 282.50
Alternative method
Use the formula for the final amount
Substitute P = 20 000, r = 15 and n = 3 into the formula
£12 282.50
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