A. There is a certain way of adding and subtracting percentages to take account of the Mark up function. Casio logic dictates certain conventions when using the % button for example:
4+17.5% calculates the sale price to make a 17.5% profit margin.
4 x 17.5%+ adds 17.5% to 4.
If you need to work out just the percentage omit the + from the end of the equation and if you need to subtract the percentage substitute the + for -.
Pressing
[Start value] + [percentage value] %
gives the selling price to make a margin of the required percentage e.g. 100 + 20% gives a selling price of £125 because £25 is 20% of £125.
Pressing
[End value] – [Start value] %
gives the percentage increase from the start value to the end value
These features are useful for accountancy purposes and are present on most Casio desktop calculators.