How to Do Percentages

When you hear lines such as "There was a 20 percent rise in rainfall this year', 'Dow Jones fell by 5 percent', 'The loan interest rates rose by 2%', they make no sense unless you know what percentage means and how it's calculated. You don't need to be a mathematics wizard to be able to compute them. All you need to know are some basic arithmetic operations.

The literal meaning of 'percentage' is 'per 100 parts'. In actuality, it is a ratio of a part, to a whole, which has been divided into hundred parts. Suppose you buy a plum cake from a bakery and divide it into 100 exact parts. If you eat 5 pieces, then one could say that you ate 5 percent of the cake.

The accepted symbol used to denote percentage is '%'. In technical terms, percentage denotes a ratio of a fraction to a whole. So the central idea which you must grasp is that calculating percentage is computing the proportion of a part to a whole, which is split into hundred parts.

Words cannot really do justice, when it comes to explaining mathematics. A math concept is best explained through equations and formulas. The true language of mathematics is expressed through symbols, formulas, and equations. The formula for calculating percentage is :

Percentage (%) = (Part/Whole) x 100

Using the formula, you can convert any ratio or fraction into a percentage. Essentially, multiplying any ratio or fraction by 100 gives you the percentage. The same formula can be used to calculate the fraction (part of the whole) from the percentage value. To do that just multiply the 'whole value' by the percentage.

For example, 80% of 200 would be :

(80/100) x 200 = 160

Let us see how to find the percentage, using the mentioned formula.

Here are some examples which illustrate how to figure out percentages:

• 3/10 x 100 = 30%
• 80/160 x 100 = 50%
• 45/180 x 100 = 25%
• 5/50 x 100 = 10%

Let us consider a word problem.
Consider that a bottle had 150 ml of water and you added 30 ml more. What is the percentage increase in water volume?
Referring to the formula, the 'part' added here is 30 ml, added to 150 ml of water. So the percentage increase would be :

30 ml / 150 ml x 100 = 20%
So one could say that there was a 20% increase in water volume.

Calculators make our life simple and computing percentages using these devices is extremely simple. Suppose a student scored 450 marks out of a total of 600 and you need to calculate his percentage score, using a calculator. How do you do it?

Using the formula, to calculate percentage, you must divide 450 (part) by 600 (whole) and multiply by 100.
Now enter the value 450 on the calculator, then hit the division sign and enter 600. After this, hitting the '=' sign will give you the value of the ratio=(450/600).
Now, hit the 'X' sign and enter 100. Hit the '=' sign again to know the percentage.

It is all just a matter of carrying out one single division and a multiplication. Practice solving four to five examples everyday, for a week and calculating percentages will never be a problem for you.