Tutorial on Percentage

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%


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