After completion of this chapter, students will be able to:

- solve the practical problems of time and work.
- solve the problems of profit and loss which includes marked price, discount, commission, and tax.
- find the compound interest on the basis of yearly system and half yearly system.
- solve the problems on population growth and compound depreciation.

The unitary method is a method or technique in an algebra for solving a class of problems in variation.Time and work are also related to the unitary method. Here, we calculate the part of a work in unit time and aslo calculate the time taken to do a work.

Profit may refer to the difference between purchase price and cost price of bringing to market. Loss can be define as the act of losing.The seller may deduct a certain amount from the price of goods. The deduction is known as discount. The price from which the discount is deducted is called the marked price or labelled price. Value Added Tax is a tax imposed by the government based on goods and services in each step of production and distribution.

Compound interest can be defined as interest calculated on the initial principal and also on the accumulated interest of previous periods of a deposit or loan. Depreciation definition, decrease in value due to wear and tear, decay, the decline in price, etc.

The growth number of the population does not remain constant. So, it is calculated in compounded way.