Percentages in Everyday Life

To find a percentage of an amount, turn the percentage into a fraction or decimal and multiply. The word 'of' means multiply.

Discount: a shirt marked R80 with $25\%$ off. The discount is $25\%$ of R80 $= \text{R}20$, so you pay $80 - 20 = \text{R}60$.

VAT: in South Africa VAT is $15\%$. On a R200 item the VAT is $0.15 \times 200 = \text{R}30$, giving a total of R230.

Percentage change: $\dfrac{\text{change}}{\text{original}} \times 100$. A taxi fare rising from R10 to R12 is a change of R2 on R10: $\dfrac{2}{10} \times 100 = 20\%$.

Exam checkpoint

For a percentage of an amount, first find 1% or 10%, then scale up. In money questions, label rands and cents in every step. Ask whether the percentage is a discount (subtract), an increase (add) or merely a portion to report. Estimation helps: 20% is about one fifth.

Short worked example. A R450 backpack has a 20% discount. Ten percent is R45, so 20% is R90. Sale price: $450-90=\text{R}360$.