We see percents all the time like when there is a sale in the mall or the supermarket, or when we give tips at the restaurant. Percent is defined as a fraction with 100 as the denominator. It means “for every hundred” or “out of a hundred”.
The (%) sign is the symbol for percent. There are two ways to write percents, you can either use the symbol form (15%) or the decimal form where you just move the decimal point two places to the left (.15). So when you see (15%) it just means 15 out of a hundred or 15/100.
There are a few ways of calculating percents, and it depends on what you are looking for:
1. Discount price. Say there’s a sale in your favorite department store. It’s 20% off on all the items, so you multiply the price of the item by 20 and then divide it by a hundred then just subtract the answer from the original price.
A Jacket is $30 with 20% off.
$3020100 = $6 (20% of $30) ,so $30- $6 = $24 (the shirt’s discounted price.)
2. Increased price. If there was 15% tax on a product you wished to buy, you multiply the price of the product by 15 and then divide it by a hundred then add the answer to the original price.
Your restaurant bill was $75 with a service charge of 15%.
$7515100 = $11.25 (15% of $75), so $75 + $11.25 = $86.25 (the total cost of your bill)
3. Getting the percentage from a ratio. Say you had a party and you wanted to know what percent of the people you invited were vegetarians. You just divide that part of the group by the total number of people then multiply it by a hundred to get the percentage.
15 out of 30 guests are vegetarian.
15 30 100 = 50%
so, 50% of the 30 guests are vegetarian.
These are the simplest and most common ways that percentages are used in daily life. If you find it too difficult do the examples above, an easy way is to find out what 1% is.
What is 7% of 42.
42100 = .42
Now we know what 1% is, we just need to multiply it by 7 to know what 7% is.
.42 7= 2.94
so, 7% of 42 is 2.94