Section 1

Finding a percentage OF a quantity

Ronaldo won 80% of the games he played.

If he played 35 games, how many games did he win?

80% of 35 is what?

This question deals with finding a percentage of a quantity when you already know the quantity and the percentage. The steps are as follows.

Put the percentage over 100 and then multiply it by 35 (the quantity)

Simplify

80/100 x 35/1

We can then simplify this to 8/10 x 35/1

Multiply the 2 fractions so we can get = 280/10

And now, divide 280 by 10 which equal 28.

So that’s all there is. Your answer is 28 which mean that Ronaldo won 28 games out of 35.

Now your turn! I want you to do the following question.

If I spent 25% of my money in Lifestyle how much do I have left if I went there with €50?

Section 2.

EXPRESS ONE QUANTITY AS A PERCENTAGE OF ANOTHER

Sometimes the information needed to solve a percentage problem is not very obvious. You will need to sort out the numbers given in the problem.

Why don’t you try organizing all the information into a box that might help you see what numbers you have and what you need?

Let’s see it in action!

There are 28 students in a class. Sixteen of those students are boys. What percentage of the class are Girls?

Boys % 16

Girls % 12

Total % 100% 28

Now, first of all we want to find out what percentage of the class are girls. But why don’t we find out what percentage of the class are boys first?

So, (Boys)

We want to find out what percentage is 16 (amount of boys in the class) is OF 28 (total amount of students in the class)

First step:

You need to put the number that you want to find out (number of boys) OVER the total number (number of student’s altogether)

16/28

Second step:

Multiply it by 100/1

16/28 x 100/1

Then all you have to do is multiply and cancel. So lets multiply straight across without cancelling.

Multiply the numerators together (top numbers)

Multiply the...