How to Do Percentages

You keep hearing about percentage all the time in the news. Lines like "There was a 20 percent increase in rainfall this year', 'Dow Jones fell by or rose by 5 percent', 'The bank loan interest rates rose by 2%', make no sense unless you know what does percentage mean and how to calculate percentage. One doesn't need to be a mathematics wizard to be able to do percentages. All you need to know are some basic arithmetic operations to be able to calculate percentage.

Mathematics supplies us with many tools which can be applied in our day-to-day life and percentage is just one of many such mathematical constructs. It is essential that you grasp what the math term - Percentage, actually means. Once you get the underlying idea of a concept, you don't have to learn it by rote. By understanding what the idea of percentage means, it will be easier for you to grasp how to calculate percentage increase or decrease.

Definition
If you ask me what the term - 'Percentage' means, the literal meaning 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 divided into 100 exact parts. If you eat 5 pieces, then I 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.

Formula
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 mathematical symbols, formulas, and equations. Here is a formula for calculating percentage:

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

Using the above formula, you can convert any ratio or fraction into a percentage. Essentially, multiplying any ratio or fraction by 100 gives you 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 me demonstrate how to find percentage, using the above formula, in the next section.

Examples
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%

Lastly, let us consider a word problem. This problem will demonstrate how to calculate percentage increase. 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 above formula, the 'part' added here is 30 ml, which was 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 the volume of water.

On a Calculator
Calculators make our life simple and calculating percentages using these devices is extremely simple. Suppose a student scored a total of 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 above formula, to calculate percentage, you must divide 450 (part) by 600 (the whole) and multiply it by 100. So first enter the value 450 on the calculator, then hit the division sign and enter 600. After this, hit the '=' sign, which will give you the value of the ratio - (450/600). Next hit the 'X' sign and enter 100. Hit the '=' sign again to know the percentage. It is as simple as that!

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