A line is missing from the purchase sheet: find the amount from the total
By Erik Nilsen · Kroni2 min read
If your child knows the final payment and every line except one, you can work out the missing amount. This is a useful check, but arithmetic does not automatically identify the item. Confirm the contents before naming the line.
Subtract known parts from the confirmed total
In a hypothetical example, payment shows 67 units. Your child's purchase sheet lists an item at 25, another at 18 and delivery at 4. One item line is missing. The arbitrary amounts are invented, and the exercise assumes no further fees or discounts.
The known parts total 25 + 18 + 4 = 47. The missing amount must therefore be 67 − 47 = 20 units. Check with 25 + 18 + 20 + 4 = 67.
First write “unknown line: 20” rather than guessing an item name. Look at the receipt or order confirmation to identify what was actually purchased. The total alone cannot distinguish an item, a charge or several smaller lines.
Check the assumption when something disagrees
A practical snag is delivery being copied incorrectly. If it actually cost 6, the remainder becomes 67 − 25 − 18 − 6 = 18 rather than 20. The same total can give another answer when a known part changes.
If multiple lines are missing, you find only their combined amount. A remainder of 20 could, for example, consist of 8 + 12; you cannot determine that split without more information.
Your child has already paid 67 altogether in this example. The unknown line forms part of that 67 rather than a new expense to deduct again. Keep the checking worksheet separate from the money entry.
Ask your family: “Have we found one missing line, or only the combined amount of everything still unknown?”
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.
