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Calculating Percentages
By Anonymous on Thursday, July 29, 1999 - 09:19 pm:

I am brain dead today and I know this should be very easy. . .Let's say I have two different numbers, x and y, and x is greater than y. How can I calculate how much bigger x is than y in terms of a percentage?

By Mike Pearson (Gmp26) on Friday, July 30, 1999 - 01:40 pm:

'How much bigger?' is easy - that's (x-y). Unfortunately it is not always obvious whether you are interested in finding (x-y) as a percentage of x giving 100(x-y)/x, or of y giving 100(x-y)/y. Which you choose depends on the context. A percentage change in salary would be calculated as a percentage of the initial salary. Similarly for a percentage increase in the cost of an item. In the business world however, it is common to calculate the profit margin of a product as a percentage of the final selling price. This would mean, for example, that a 50% margin actually means that the selling price is twice the cost! Marketing executives don't like to sound as if they are making excessive profits!

By Anonymous on Friday, July 30, 1999 - 06:08 pm:

I'm comparing two numbers: 131,721 and 7,729. What different comparison statements can be made about the two numbers using percentages, and how can I calculate those percentages? Specifically, I wanted to know how much bigger 131,721 is in terms of a percentage.

Thanks!

By Anonymous on Friday, July 30, 1999 - 06:30 pm:

The number 131721 is a little more than 17 times the number 7729 and, comparing the two numbers, 131721 is 1704% of 7729 (this is a multiplicative scaling factor). The increase, that is the difference between the two numbers, is 123992 which is 94% of 131721 and 1721% of 7729.

By Graham Lee (P1021) on Wednesday, September 8, 1999 - 07:29 pm:

As a percentage is relative, you can work in terms of either. Remember to check the individual question to see if you should give one method above the other. For instance:

I can buy a car in France for £8000 when it costs £10000 in England. What is the percent saved?

In this case, you should give the percentage in terms of the higher price, as this shows how much of the English cost you have saved by going to France.
(10000-8000)/10000
=2000/10000
=1/5=20%.

If you did
(10000-8000)/8000
=2000/8000
=1/4=25%
you would have the increase of the English price over the French price expressed as a percentage, which is incorrect.

GL