Two successive discounts do not add up to their percentages
By Erik Nilsen · Kroni3 min read
When two discounts are applied one after another, the second is calculated from a new, lower price. Your child cannot simply add the percentages together. Instead, draw a short price ladder showing the cost at each step.
Calculate one step at a time
In an imaginary offer, an item costs 200 units before any discount. First, 20 per cent is taken off. A code then gives another 10 per cent off the reduced price. This uses arbitrary teaching units and an invented offer; read the actual conditions before using any real code.
The first discount is 200 × 0.20 = 40 units. The new price is 200 − 40 = 160 units. The second discount is 160 × 0.10 = 16 units. The final price is 160 − 16 = 144 units. The total saving is 40 + 16 = 56 units.
If your child adds 20 and 10 per cent instead, the imagined discount is 30 per cent of 200, or 60 units. That produces an answer of 140. The difference of 4 units comes from the last discount being calculated on 160 rather than 200.
Write the starting amount beside each discount: “20 per cent of 200” and “10 per cent of 160”. For a younger child, draw ten boxes to represent each price. One box means 20 units at first and 16 units after the first discount.
Check what the code actually covers
A realistic snag is that a shop may not allow the code alongside another offer. The calculation then does not establish that you can buy the item for 144 units. It only gives that result if both discounts really apply in the order described.
Ask your child to read the basket total and compare it with the ladder. If the numbers differ, find the explanation before paying: the discount's starting amount, excluded products, or delivery. Do not proceed simply because the difference seems small.
Finish by testing an easier starting price of 100 units. The first reduction leaves 80; the next leaves 72. The combined discount is still 28 per cent, but the saving is now 28 units. That separates the percentage from the amount of money saved.
Ask your family: “Which amount is the last discount calculated from, and where can we see it?”
Carry the calculation into your family agreement
Kroni can keep track of your child's virtual balance. The app does not transfer money, so any actual purchase is paid for outside it. Agree on what you will record, then check the amount with your child afterwards. Do not deduct a possible cost as though the purchase had already happened. Read about allowance in Kroni.
