大象传媒

PercentagesAppreciation/depreciation

Calculations can be carried out using percentages of shapes and quantities. We can calculate percentage increase and decrease, as well as express a quantity as a percentage of another quantity.

Part of Application of MathsNumeracy skills

Appreciation/depreciation

The value of a house is usually said to increase with time. Therefore its value is said to appreciate.

Example 1

A flat bought for \(\pounds74\,000\) in 2005 appreciated in value each year by \(1.5\%\).

Calculate the value of the flat after four years.

\({(1.015)^4} \times 74000\)

\(= \pounds78540.90\)

The value of the flat after four years is \(\pounds78\,540.90\).

The value of a car however is usually said to decrease in value with time. Therefore its value is said to depreciate.

Example 2

Jack and Trisha bought a new car for \(\pounds8500\) in 2008. In the first year, its value depreciated by \(20\%\), in the second year by \(15\%\) and in the third by \(10\%\).

Calculate the value of the car at the end of each year.

Value at the end of Year 1:

Percentage has gone down by \(20\%\), therefore \(100\% - 20\% = 80\%\)

\(80\% \,of\,8500\)

\(= 0.8 \times 8500\)

\(= \pounds6800\)

Value at the end of Year 2:

Percentage has gone down by \(15\%\), therefore \(100\% - 15\% = 85\%\)

\(85\% \,of\,6800\)

\(= 0.85 \times 6800\)

\(= \pounds5780\)

Value at the end of Year 3:

Percentage has gone down by \(10\%\), therefore \(100\% - 10\% = 90\%\)

\(90\% \,of\,5780\)

\(= 0.9 \times 5780\)

\(= \pounds5202\)

Now try this:

Question

Jean bought an antique brooch for \(\pounds200\). Its value appreciates by \(10\%\) each year.

Calculate the value of the brooch after 10 years.

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