To calculate 10% of a quantity, we simply divide by 10.
Many other percentages can be found using mental arithmetic.
| 1% | Divide by 100 |
| 10% | Divide by 10 |
| 5% | Find 10% then half that. |
| 15% | Find 10%, find 5% then add them together. |
| 50% | Divide by 2. |
| 25% | Find 50% then half that. |
| 95% | Find 5% then subtract that from the total. |
| 12% | Tax in BC (GST + PST). Find 10%. Find 1%, double it. Add to get 12. |
Being able to calculate a few of these percentages mentally adds to general numeracy – another building block to confidence when you’re out and about, at home or at work.
15 questions correct wins you a star!
Or, if you happen to be using a calculator, we would perform the following calculations:
| 1% | Multiply by 1/100 |
| 10% | Multiply by 10/100 |
| 5% | Multiply by 5/100 |
| 15% | Multiply by 15/100 |
| 50% | Multiply by 50/100 |
| 25% | Multiply by 25/100 |
| 95% | Multiply by 95/100 |
| 12% | Multiply by 12/100 |
For example, to calculate BC sales tax (12%) on an item that costs $90:
90 multiply by 12 divide by 100 = 10.80
The sales tax is $10.80. Therefore the total cost is 90.00 + 10.80 = $100.80.
As another example, suppose we wish to find 11% of 185.
We type into the calculator: 185 multiply by 11 divide by 100 to get 20.35.