Successive discounts are applied one after another to a shrinking base. A 20% discount followed by 10% produces a 28% effective discount—not 30%.
Convert every discount to a remaining-price factor, multiply the factors, then subtract the result from one.
Start from a list price of €100. The first 20% discount reduces it to €80. The second 10% discount applies to €80, not to the original €100, and reduces the price to €72.
For 20%, 10% and 5% discounts, multiply 0.80 × 0.90 × 0.95 = 0.684. The final price is 68.4% of list price, so the effective discount is 31.6%, not 35%.
Adding headline percentages overstates the concession and distorts the real purchase or selling price. Use the same sequence shown in the offer, separate discounts from fees, and include free goods only after translating them into their economic effect. BusyFella applies discounts progressively so each percentage works on the result of the previous step.