The formula for percentage is the following and it should be easy to use:

Study it below carefully before looking at the examples

\(\frac{is}{of}= \frac{%}{100}\)

OR

\(\frac{part}{whole} = \frac{%}{100}\)

We will take examples to illustrate.Let us start with the formula on the left

An important thing to remember: Cross multiply

It means to multiply the numerator of one fraction by the denominator of the other fraction

Examples #1:

25 % of 200 is____

In this problem, of = 200, is = ?, and % = 25

We get:

is/200 = 25/100

Since is in an unknown, you can replace it by y to make the problem more familiar

y/200 = 25/100

Cross multiply to get y × 100 = 200 × 25

y × 100 = 5000

Divide 5000 by 100 to get y

Since 5000/100 = 50, y = 50

So, 25 % of 200 is 50

Examples #2:

What number is 2% of 50 ?

This is just another way of saying 2% of 50 is___

So, set up the proportion as example #1:

is/50 = 2/100

Replace is by y and cross multiply to get:

y × 100 = 50 × 2

y × 100 = 100

Since 1 × 100 = 100, y = 1

Therefore, 1 is 2 % of 50

Examples #3:

24% of___ is 36

This time, notice that is = 36, but of is missing

After you set up the formula, you get:

36/of = 24/100

Replace of by y and cross multiply to get:

36/y = 24/100

y × 24 = 36 × 100

y × 24 = 3600

Divide 3600 by 24 to get y

3600/24 = 150, y = 150

Therefore, 24 % of 150 is 36

Now, we will take examples to illustrate how to use the formula for percentage on the right

Examples #4:

To use the other formula that says part and whole, just remember the following:

The number after of is always the whole

The number after is is always the part

If I say 25 % of___ is 60, we know that the whole is missing and part = 60

Your proportion will will like this:

60/whole = 25/100

After cross multiplying, we get:

whole × 25 = 60 × 100

whole × 25 = 6000

Divide 6000 by 25 to get whole

6000/25 = 240, so whole = 240

Therefore, 25 % of 240 is 60

Examples #5:

___% of 45 is 9

Here whole = 45 and part = 9, but % is missing

We get:

9/45 = %/100

Replacing % by x and cross multiplying gives:

9 × 100 = 45 × x

900 = 45 × x

Divide 900 by 45 to get x

900/45 = 20, so x = 20

Here we go!. I hope these formula for percentage were helpful.

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