• Ratio: Comparing by division is called ratio.
  • Quantities written in ratio have the same unit.
  • Ratio has no unit.
• Proportion: Equality of two ratios is called Proportion.
• Product of extremes = Product of means
• Percentage: Percentage means for every hundred. The result of any division in which the divisor is 100 is a percentage. The divisor is denoted by a special symbol %, read as percent.

Profit and Loss

• Cost Price (CP): The amount for which an article is bought.
• Selling Price (SP): The amount for which an article is sold.
• Overhead expenses are additional expenses made after buying an article are included in the cost price.
• Discount is a relaxation offered on marked price. Discount = Marked Price – Sale Price.
• Discount can be calculated when discount percentage is given. Discount = Discount % of Marked Price
• CP = Cost price + overhead expenses.
• Sales tax is charged on the sale of an item by the government and is added to the Bill Amount. Sales tax = Tax% of Bill Amount
• Simple Interest: If the principal remains the same for the entire loan period, then the interest paid is called simple interest.
  • SI = (P X R X T)/1000
• Compound Interest is the interest calculated on the previous year’s amount (A= P+I)
  • Amount when interest is compounded annually = P(1 + R/100)ⁿ; P is principal, R is rate of interest, n is time period.
  • Amount when interest is compounded half yearly = P(1 + R/100)²ⁿ; R/2 is half yearly rate and 2n = number of ‘half-years’