To multiply percentages you need to work in a very similar way to multiplying normal whole numbers.
If you are multiplying a percentage, you need to understand that the number you have is 100%. If you wish to add 20% to this, you will then have 120%. Getting your head around the percentage being 100 rather than a number itself is the hardest thing when you start multiplying percentages.
If you have $40 and you wish to add another 20% on to this, you just need to multiply what you already have you need to do the following calculation.
40 x 1.20
This will give you 120% and therefore you will have multiplied the percentage. This new figure, if it is to be a whole amount, will then turn into 100%.
- Multiplying parts of percentages
If you then wish to add another 10% to your original amount, you should do the same thing again with the $40 as your 100% and then you will have to add the 10% and the 20% together. This will make a 30% increase.
- Reasons for multiplying percentages
There are many reasons why you would want to multiply a percentage. You may need to add on interest and see how this will accumulate interest on top of what is already there. You will have a different figure acting as 100% each time as this rises and you may want to keep a running total on a spreadsheet is this is what you are multiplying for. This will make it less confusing if the percentage that you are working to changes at any point and you have to alter your multiplication calculation.
