Twice the price is 200 per cent of the price, not 200 per cent more
By Erik Nilsen · Kroni2 min read
“Of” and “more” describe different percentage calculations. Your child may intend the same thing in conversation yet produce different amounts on paper. Write both the price and the increase before using a percentage phrase.
Compare twenty with forty
In a hypothetical example, a simple personal item costs 20 units and another version costs 40. The arbitrary figures are invented. The expensive version costs 40 / 20 = 2 times as much, or twice the price.
Forty is 200 per cent of twenty because 20 × 2 = 40. However, the increase is 40 − 20 = 20. Relative to the first price, the increase is 20 / 20 = 100 per cent. The item therefore costs 100 per cent more rather than 200 per cent more.
“200 per cent more than twenty” would add twice the original price: 20 + 2 × 20 = 60. That is three times the original price.
Check the words against an amount
A practical snag is saying “two hundred per cent more” while pointing at 40. Ask which part represents 200 per cent: the whole new price or only the addition? Here it represents the whole price.
With a budget of 45, an item at 40 fits while one at 60 does not. An imprecise percentage phrase can therefore create a different budget from the actual price label.
Use “costs twenty more” when that adequately explains the decision. Every comparison need not contain a percentage. For an actual purchase, check the price and contents rather than only someone's description of the difference.
Ask your family: “Does the percentage describe the entire new price or the increase from the old one?”
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.
