Multiplying fractions. Finding a fraction from a number

Multiplying fractions: multiply numerators together and denominators together. Cancel common factors between numerators and denominators before multiplying (“cross-cancel”) or after — it is always good to write the answer in fully reduced form. A fraction of a number is the same as multiplying the number by the fraction: for example,

\frac{2}{5}

15

15\times\frac{2}{5}

Rule:

\frac{a}{b}\cdot\frac{c}{d}=\frac{ac}{bd}

(do not forget to reduce)

\frac{m}{n}

A

A\cdot\frac{m}{n}

A whole number can be written as

\frac{k}{1}

when multiplying by a fraction

Multiplying two fractions: explained

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