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% Percent : Percentages Explained %


The business of Percent (%) is quite easy to understand, but I realised recently that not everyone understands percentages. According to someone in the know, "Less than 10% of people understand percentages". Well, that could be about to change, as I intend to explain percentages so most people can understand them.

The "cent" in "percent" means "hundred", as in words like century, centurion, and cent. Per-cent is in effect "parts per hundred". So, for example, if there are 100 marbles in a bag and only one of them is blue, then that's 1% (one percent) that are blue. If the bag was bigger and there were 1000 marbles and 1% of them were blue, then as one in every hundred are blue, then there'd be about 10.

If 8 out of 10 cats said they preferred some particular type of catfood, then that's 80% of cats (because it's 80 out of every 100 cats).

Percentages are like portions or fractions but made 100 times bigger to make them easier to talk about. If less than a fifth of the population support the war, then it's equivalent to "less than 20% of the population support the war".

You sometimes see percentages in the business of finance, for example, an interest rate of 5%. If you get 5% interest on your savings, then that means that you get 5.00 for every 100.00 invested. So, if you invest 2000.00, you get 5% of that as interest, which is five x 1/00 x 2000 = 100.00 , so (if it's per annum / per year), then you have 2100.00 at the end of the year in total.

If 15% vat (purchase tax) is added on the price of goods, then the total cost is 1.15 times the original price.

You have to be careful of percentages that are cumulative. For example, if someone offers you a loan which is charged at 3% per month, then what happens is that with each passing month you owe 1.03 times as much as the month before. After twelve months that's 1.03 x 1.03 x 1.03 x 1.03 x 1.03 x 1.03 x 1.03 x 1.03 x 1.03 x 1.03 x 1.03 x 1.03 (or 1.0312) which is 1.426 , or to put it another way, it's 42.6% interest per year. This sort of thing is why APR (Annual Payment Rate) statements were made standard. You can calculate APR easily and compare it.

Percentages are sometimes used in expressing probability. For example, "There's an 80% chance it will snow this weekend". This doesn't mean that it will snow, or that it won't. It means that it is very likely to snow. If people understood percentages, then weather forecasters would be able to say things about the weather in that sort of way, in terms of percent probabilities, which would be much more realistic than the simple prediction as if they know exactly what's going to happen!

There's sometimes a misunderstanding about what fifty-fifty means. A 50:50 means that there's a 50% chance that something will happen. 50% is half. Like the toss of a coin, there's an equal chance it will come down either side. This is not because there are two sides to the coin. If you buy a lottery ticket, there are two possibilities: you might win, or you might not. This doesn't mean it's 50:50, obviously. The coin is 50:50 because the two sides are equally likely.

The percent sign (%) is reputed to be a composite of divide (/) and the figure 100 split across it. Such symbols go back a long way, at least to the time of typewriters, when the @ symbol wasn't part of e-mail but instead was used in the context of "4 candles @ sixpence each" = "four candles AT sixpence each" in tallies and receipts, usually handwritten, and sometimes with a 2d stamp on them.

Percentages have to add up to 100%. There's no such thing as "putting 110% effort in". 100% is like a cake at a party divided into slices. Once the whole cake has been shared out, that's all there is.

A bottle of spirits with 70 proof is sometimes misread as seventy percent proof. That's incorrect. It's 70 degrees proof. If it was 40% VOL, then it really would be 40 percent alcohol.


Another interesting review at Zyra's website. There are many more pages, over nine thousand in fact. So, if you have read 90 of them, that's less than 1%.