Percentages
Last updated: 11 Nov 2008
Percentages are a real favourite of the GMAT question writers. You must be comfortable with them if you are to do well in the test.
Percent means per hundred and therefore can easily be represented as a fraction with denominator 100.
We already saw how the most common percentages could be expressed as both fractions and decimals in the fractions tutorial.
It will make the GMAT far easier for you if you learn this table showing equivalent fractions and percentages.
Example percentage question
What is 20% of 360 ?
To calculate the percentage of a number you simply multiply the percentage by that number
...and since you did the fractions tutorials you know that
So 20% of 360 is 72.
Note: a neat trick for dividing by 5 is to first multiply by 2 and then divide by 10. In this example 360 multiplied by 2 is 720 divided by 10 is 72.
Sales and discounts
Sales and discounts are a common topic of GMAT questions. For example,
A chair normally priced at $48, is discounted by 25% in a sale. What is the chair's sale price?
In these questions you could work out the discount and then take the discount away from the original price but you can save time by going straight to the sale price. In this case a 25% discount will mean the sale price is 75% of the original.
...and you know that
The sale price of the chair is $36.
Percentage change
There are many questions that will ask you to calculate the percentage increase or decrease from one number to another.
In these cases you will have to calculate the difference and then work that out as a percent of the original number.
We will begin with an simple example, what is the percent increase from 50 to 75 ?
First calculate the difference
Then work out the percentage the difference is of the original
The percentage increase from 50 to 75 is 50%.
It is important to note that the reverse, the percentage decrease from 75 to 50 is not the same. The absolute difference is still 25 but the base number is now 75.
The percentage decrease from 75 to 50 is %.
Hi there. I wrote you about this before and it was fixed but seems to be broken again. Did something happen to the mathematical expressions again? I even tried to clear my browser, us a different browser, etc.
Thank you very much