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
A shop offers \(30\%\) off everything in a sale. The sale price of a pair of designer shoes was \(\pounds84\).
Calculate the cost of the shoes before the sale.
Sale of \(30\%\) 鈫 (\(100\%\) - \(30\% = 70\%\))
\(70\%\) of the cost of the shoes \(= \pounds84\)
\(1\%\) 鈫 \(84 \div 70 = \pounds1.20\)
\(100\%\) 鈫 拢1.20 x 100 = 拢120
The cost of the shoes before the sale was 拢120.
Now try this:
After a 4% wage rise, Bill earned 拢1248 each month.
Calculate how much Bill earned each month before the wage rise.
4% rise therefore 100% + 4% = 104%
\(104\% = \pounds1248\)
\(1\% = \frac{{1248}}{{104}} = \pounds12\)
\(100\% = 12 \times 100 = \pounds1200\)
Bill earned 拢1200 each month before the wage rise.