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Maths
Summary
It is often useful to calculate percentages of amounts when solving problems. Some are simple and some require a little more work.
There are two methods to calculating percentages of amounts: by using simple percentages that you already know, or by converting the percentage to a fraction and multiplying.
You can always split up a percentage into smaller simple ones. Below are some simple percentages that you need to remember how to calculate, as well as their equivalent fraction pairs.
PERCENTAGE | FRACTION | HOW TO CALCULATE |
$50 \%$ | $\frac{1}{2}$ | Divide by two |
$25\%$ | $\frac{1}{4}$ | Divide by four |
$10\%$ | $\frac{1}{10}$ | Divide by ten |
$5\%$ | $\frac{1}{20}$ | Divide by ten and then two |
$1\%$ | $\frac{1}{100}$ | Divide by one hundred |
In a sale, everything is $17\%$ off. What saving would be made on $£200$?
Split $17\%$ into simple percentages.
$17\%=10\%+5\%+1\%+1\%$
Work out each of the simple percentages.
$10\%$ of $200 = 200\div10=20$
$5\%$ of $200= 10\% \div 2=20\div2=10$
$1\%$ of $200= 200\div100=2$
Add together the simple percentages.
$20+10+2+2=\underline{£32}$
The second method is to simply turn the percentage into a fraction and multiply by the amount. Remember that to convert from a percentage to a fraction you take the percentage as a fraction out of one hundred.
Calculate $29\%$ of $£3300$.
Write $29\%$ as a fraction out of one hundred.
$\frac{29}{100}$
Multiply by $£3300$.
$\begin{aligned}\frac{29}{100}\times£3300=£3300 \div 100 \times 29\\=£33 \times 29 = \underline{£957} \end{aligned}$
Mean, median, mode and range
FAQs
Question: How do I work out a percentage using fractions?
Answer: Turn the percentage into a fraction and multiply by the amount. To convert from a percentage to a fraction you take the percentage as a fraction out of one hundred.
Question: How do I work out 1% of a number?
Answer: To work out 1% of a number, divide by one hundred.
Question: How do I work out 10% of a number?
Answer: To work out 10% of a number, divide by ten.
Question: How do I work out 50% of a number?
Answer: To work out 50% of a number, divide by two.
Question: How do I find a percentage of an amount?
Answer: There are two methods to calculating percentages of amounts: by using simple percentages that you already know, or by converting the percentage to a fraction and multiplying.
Theory
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