To increase £50 by 10%, we can calculate 10% of £50 and add the answer.

£50+£5=£55

We could have obtained the same answer by multiplying £50 by

\[1+10\%=1+\frac{10}{100}=1.1\]

This method is especially convenient when an amount increases several times by different percentages.

Suppose £50 is increased in turn by 10%, 15%, 20% and 25% in steps.

To increase by 10% multiply by

\[1+10\%=1+\frac{10}{100}=1.1\]

To increase by 15% multiply by

\[1+15\%=1+\frac{15}{100}=1.15\]

To increase by 20% multiply by

\[1+20\%=1+\frac{10}{100}=1.2\]

To increase by 25% multiply by

\[1+25\%=1+\frac{10}{100}=1.25\]

To increase by 10% then 15% then 20% then 25%, multiply by