Calculating Percentages

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: 180 multiply by 11 divide by 100 to get 20.35.


Done! Take me back to the Number menu.