More contents or a lower price: ten per cent does not always mean equal savings
By Erik Nilsen · Kroni3 min read
Ten per cent more contents and ten per cent off sound equally large. They change different parts of the calculation, though. Compare the cost of the same quantity, then check whether your child actually needs the larger pack.
Use the same original product
In a hypothetical example, an optional bottle of drawing material costs 20 units for 100 millilitres. Offer A gives 10 per cent more contents at the same price. Offer B takes 10 per cent off the standard bottle. The contents are otherwise identical, and the arbitrary prices are invented.
A provides 100 + 10 = 110 millilitres for 20 units. B provides 100 millilitres for 20 − 2 = 18 units. To compare quantity prices, calculate A per 100 millilitres: 20 / 110 × 100, approximately 18.18 units. B costs 18 units per 100 millilitres.
The price reduction therefore gives a slightly lower quantity price in this example. There is no need to pretend the difference is large: it is approximately 0.18 units per 100 millilitres. The calculation nevertheless shows that the two percentages do not do exactly the same job.
Check using a larger comparison quantity if decimals are difficult. Ten A bottles provide 1100 millilitres for 200 units. Eleven B bottles also provide 1100 millilitres, costing 11 × 18 = 198 units. The same quantity then costs 2 units less with B. This is a calculation exercise, rather than a suggestion to buy lots of bottles.
Let the need determine the actual purchase
If your child needs only 100 millilitres, B meets the need for 18 units. If they genuinely need 110 and only whole bottles are sold, one A bottle may be simpler than two B bottles. Comparing quantity prices and choosing the number of bottles are separate steps.
A realistic snag is the extra contents or discount applying to a different material. Check that both offers provide the same usable product before calculating. Different properties need separate consideration rather than being hidden behind a percentage.
Ask your family: “Which offer has the lowest price for the same quantity, and which meets our exact need with the smallest payment?”
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.
