- To compare two quantities, their units must be the same.
- Two ratios can be compared by converting them into like fractions.
- If the two fractions are equal, we say that the two given ratios are equivalent.
- If two ratios are equivalent (or equal), then the involved four quantities are said to be in proportion.
- One of the ways of comparing quantities is percentage.
- Per cent is derived from Latin word ‘per centum’ meaning ‘per hundred’.
- Percent is represented by the symbol % and means hundredth too.
- Fractions can be converted into percentages and vice-versa.
- Decimals can also be converted into percentages and vice-versa.
- The buying price of any item is known as its cost price.
- It is written in short as CP.
- The price at which an item is sold, is known as its selling price or in short SP.
- If CP < SP, then a profit is made and Profit = SP – CP.
- If CP = SP, there is no profit or loss.
- If CP > SP, then a loss is made and Loss = CP – SP.
- Profit per cent = Profit / CP ×100
- Loss per cent = Loss/CP ×100
- ‘Principal’ P, means the borrowed money.
- The extra money paid by borrower for using borrowed money for given time is called ‘Interest’ I.
- The period for which the money is borrowed is called ‘Time Period’ T.
- To determine Interest to be paid, we have ‘Rate of Interest’.
- Rate of Interest is generally given in per cent per year.
- On a principal of P at R % rate of interest per year, the interest (simple) I paid for T years is given by

P× R × T / 100 =I - The total money paid alongwith interest or principal P is called amount (A). Thus A = P + I.

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