Percentage change as a multiplier

How to use it

1. 1Chain successive changes by multiplying factors, never by adding percentages.
2. 2A rise of $p\%$ followed by a fall of $p\%$ gives $1-\frac{p^2}{10^4}$, a net loss.
3. 3Reverse a change by dividing by the factor, not by applying the opposite percentage.

Step-by-step

1. 1
   $1.20\times 0.80=0.96$

   Why: Multiply the factors; percentages do not add.

2. 2
   $0.96\Rightarrow$ a $4\%$ decrease