Rounding each line or the final total: a small difference can be valid
By Erik Nilsen · Kroni2 min read
Two calculations can give slightly different answers if you round at different stages. When your child checks a decimal price, write the rounding rule used by the exercise before comparing it with another result.
Decide the rounding rule first
In a hypothetical example, three items each cost 1.25 units before a 10 per cent reduction. The figures and rules are invented. On this worksheet amounts are rounded to two decimal places, to the nearest hundredth and upwards at an exact halfway point. This makes no claim about shop or Kroni rounding.
After the reduction, each item costs 1.25 × 0.90 = 1.125. Rounded per item, that becomes 1.13. Three rounded lines give 3 × 1.13 = 3.39 units.
Calculating the order together first, the original total is 3 × 1.25 = 3.75. After the reduction it is 3.75 × 0.90 = 3.375. Rounding once at the end produces 3.38 units.
The difference is 3.39 − 3.38 = 0.01. You have not necessarily missed an item or used the wrong percentage. You have selected different rounding stages.
Keep extra digits during calculation
A practical snag is comparing rounded worksheet lines with a total calculated without intermediate rounding. Label the first “rounded per item” and the second “rounded after addition”.
If you are practising final-total rounding, retain 1.125 during the calculation. Do not change it to 1.13 before all items are added. For an actual purchase, ask how the final amount was calculated if a difference needs explaining.
The receipt's confirmed payment is the purchase amount to record. Your checking worksheet should not create an additional expense or an invented claim for a refund.
Ask your family: “Did we round at the same stage using the same rule before comparing answers?”
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.
