Formula for percentage

The formula for percentage is the following and it should be easy to use if you follow the straightforward directions given.





Study it below carefully before looking at the examples

Formula for percentage


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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