Chained discounts
What several discounts on one price are really worth together.
How this works
Discounts do not add up. The second one comes off what is left, not off the original price, so 20 and then 10 is 28 rather than 30. On a quotation reading 20 plus 10 that is two per cent of every order, in the supplier's favour.
The order does not change the final price. It only changes what the figures in between look like.