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Two simple ratios are expressed like a single ratio as the ratio of product of antecedents to product of consequents and we call it Compound ratio of the given two simple ratios. a:b and c:d are any two ratios, then their compound ratio is a/b × c/d = , i.e. ac:bd.

A percentage (%) compares a number to . The word percent means "per every hundred" or "out of every hundred". 100% = it is also a fraction with denominator 100.

Discount is a decrease percent of marked price. Price reduction is called Rebate or discount. It is calculated on marked price or List Price.

Profit or loss is always calculated on price. Profit is an example of percent of cost price and loss is an example of percent of cost price.

VAT will be charged on the price of an item and will be included in the bill. VAT is an increase percent on Selling Price.

Simple interest is an increase percent on the Principal

Simple Interest (I) = P×T×R100 where P = principal T = Time in years R = Rate of Interest.

Amount = Principal + Interest = P + P×T×R100 = P(1 + T×R/100)

Compound interest allows you to earn on interest.

Amount at the end of 'n' years using compound interest is A = P(1 + R/100)ⁿ

The time period after which interest is added to principal is called period. When interest is compounded half yearly, there are conversion periods in a year, each after 6 months. In such a case, half year rate will be of the annual rate.