Percents

Calculating Percentages

Calculating percent problems

There are many times in real life when you may need to calculate a percentage. You might need to figure out how much money a 5% discount will save you, or how much interest you'll pay on a loan with a 6% interest rate. Knowing how to calculate percentages will help you in both of these situations.

Setting up the calculation

Let's say the mailing department was responsible for 25% of the accidents at your company this year. There were 80 accidents total, and 20 of them were in the mailing department. You could write that like this:

25% of 80 = 20

This expression tells you that 25% of 80 is equal to 20. But what if you don't know how much a percentage is equal to? Let's say the demolition department was responsible for 50% of the 80 accidents. You don't know how many accidents 50% of 80 is. So you could write that like this:

50% of 80 = ?

To figure out what 50% of 80 is, you'll need to rewrite this example so it can be solved with math.

Click through the slideshow to see how to set up the example as a mathematical expression.

We need to turn this example into something we can solve with math.
First, we'll deal with the word of. Whenever you see that word in a percentage problem, it usually means multiplication.
First, we'll replace the word of with a multiplication sign.
Now we need to convert our percentage into a decimal. We'll do that by inserting a decimal point after the 50...
We'll do that by inserting a decimal point after the 50...and moving it two places to the left.
Now we have an equation we can use math to solve. All we have to do is multiply 0.50 by 80.
Let's set up another example. This time we want to find 7% of 120.
First, we'll replace the word of with a multiplication sign.
We'll turn our percent into a decimal. We'll insert our decimal point after the 7...
We'll turn our percent into a decimal. We'll insert our decimal point after the 7...and move it two spaces to the left.
Now we've set up an equation we can solve with math.