Percentage is another way of expressing fractions.
In percentage we represent fractions with 100 as the denominator.
For example 1/2 = 50/100. This in percentage is called 50%.
1/2 can be expressed as a decimal as 0.50.
1/2, 50% and 0.50 all mean the same.
So to convert 0.50 in percentage we multiply the decimal by 100 and put a % sign.
This is how we would convert any decimal into a percentage for example 0.75 x 100 = 75%.
To convert a fraction to percentage we first convert the fraction into a decimal and then into percentage.
For example 3/4 = 0.75 = 75%.
Interest and Discount
Percentages are useful here as they are used for
expressing rates of interest.
The formula is
Interest = Amount x Time x Rate
For example if we want to find out how much interest will $1000 earn in 1yr at an annual interst rate of 6%.
6% = 6/100
(6/100)x 1000 = 60
So the answer is $60
Another example: How much interest will $1000 earn in 6 months at an annual rate of 6%.
Here we use the formula
Interest = Amount x Time x Rate
6 months is 1/2 of a year
6 % is 6/100 or 3/50
Using our formula: Interest = $1000 x 1/2 x 3/50 = $30
The annual rate is for 12 months
We are looking at 6 months
This type of interest calculation is called Simple Interest
For Discount the formula is:
Discount = Cost x Rate of Discount
For example what is discount if a car costing $5000 is discounted at 5%?
5% is = 0.05
Discount = 0.05 x $5000 = $250
Another formula gives us the Rate of Discount
Rate of Discount = (Cost – Price) / Cost
What would be the discount if a car costing $6000 is sold for $5400
Rate of Discount = (6000 – 5400)/6000 = 600/6000 = 10/100 or 10%