A fraction is made up of:
$$ \dfrac{numerator}{denominator} $$
To write a fraction as a decimal, divide the top number by the bottom number:
$$ \dfrac{1}{2} = 1\div2 = 0.5 $$
To divide a fraction, turn it upside down and multiply:
$$ \dfrac{1}{2} \div \dfrac{3}{4} = \dfrac{1}{2} \times \dfrac{4}{3} = \dfrac{4}{6} = \dfrac{2}{3} $$
When adding and subtracting fractions, the denominators must be the same
$$ \dfrac{1}{2} + \dfrac{3}{4} = \dfrac{2}{4} + \dfrac{3}{4} = \dfrac{5}{4} = 1\dfrac{1}{4} $$
To convert a fraction to a decimal, divide the numerator by the denominator
To convert a decimal to a fraction, place the decimal number over the place value
$$ 0.65 = \dfrac{65}{100} = \dfrac{13}{20} $$
The first significant figure is the first non-zero digit in a number
$$ 1361 \,\textrm{to}\, \,\textrm{2 s.f.}\, = 1400 $$
For decimal places count after the decimal point from left to right
$$ 7.1361 \,\textrm{to}\, \,\textrm{2 d.p.}\, = 7.14 $$
$x$ as a percentage of $y$
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