Mathematics -- Class 4

Topic: Unitary Method
Name: ____________________________Class: 4Date: ________________
Learning Objectives
Let Us Begin!

Kavita goes to a stationery shop near her school in Jaipur. She sees a sign: "5 pencils for Rs 30." She wants to buy 8 pencils. How much will she pay?

To solve this, we first find the cost of 1 pencil, and then multiply to find the cost of 8 pencils. This clever method is called the Unitary Method because we always find the value of one unit first.

Step-by-Step Explanation

What is the Unitary Method?

The unitary method is a way of solving problems where we first find the value of 1 unit (one item), and then use it to find the value of the number of units we need.

Step 1: Find the Value of 1 Unit

If we know the cost of several items, we divide to find the cost of 1 item.

Example: 5 pencils cost Rs 30. Cost of 1 pencil = Rs 30 / 5 = Rs 6.

Think about it: Why do we divide? Because we are splitting the total cost equally among all the items.

Step 2: Find the Value of the Required Number of Units

Once we know the cost of 1 item, we multiply to find the cost of as many items as we need.

Cost of 8 pencils = Rs 6 x 8 = Rs 48.

Think about it: Why do we multiply? Because if 1 item costs Rs 6, then 8 items will cost 8 times as much.

The Two Steps -- Always Remember

StepWhat We DoOperation
Step 1Find the value of 1 unitDivide
Step 2Find the value of the required unitsMultiply

Writing the Solution Neatly

Always write your solution in this format:

Cost of 5 pencils = Rs 30

Cost of 1 pencil = Rs 30 / 5 = Rs 6

Cost of 8 pencils = Rs 6 x 8 = Rs 48

Think about it: Rohan buys 4 notebooks for Rs 120. His sister wants 7 notebooks. Can you find the cost? What will you do first?

Key Words and Meanings
WordMeaning
Unitary methodA method where we first find the value of 1 unit, then find the value of many
UnitOne single item or thing
Cost priceThe amount of money needed to buy something
DivideTo split equally into parts
MultiplyTo add a number to itself a certain number of times

Mathematics -- Class 4 (continued)

Topic: Unitary Method -- Examples and Practice
Examples
Example 1: Cost of Mangoes

6 mangoes cost Rs 90. Find the cost of 10 mangoes.

Cost of 1 mango = Rs 90 / 6 = Rs 15

Cost of 10 mangoes = Rs 15 x 10 = Rs 150

Example 2: Cost of Notebooks

3 notebooks cost Rs 45. Find the cost of 9 notebooks.

Cost of 1 notebook = Rs 45 / 3 = Rs 15

Cost of 9 notebooks = Rs 15 x 9 = Rs 135

Example 3: Cost of Bangles

A shopkeeper in Hyderabad sells 4 bangles for Rs 60. Sita wants to buy 7 bangles. How much will she pay?

Cost of 1 bangle = Rs 60 / 4 = Rs 15

Cost of 7 bangles = Rs 15 x 7 = Rs 105

Key Points to Remember
Practice Questions

A. Fill in the Blanks

  1. In the unitary method, we first find the value of unit.
  2. To find the cost of 1 item, we the total cost by the number of items.
  3. To find the cost of many items, we the cost of 1 item by the number needed.
  4. If 4 erasers cost Rs 20, the cost of 1 eraser is Rs .
  5. If 1 pen costs Rs 12, then 6 pens cost Rs .

B. Multiple Choice Questions

  1. 8 bananas cost Rs 40. What is the cost of 1 banana?
    (a) Rs 4(b) Rs 5(c) Rs 8(d) Rs 10
  2. If 1 samosa costs Rs 8, what is the cost of 5 samosas?
    (a) Rs 13(b) Rs 30(c) Rs 40(d) Rs 45
  3. Which step comes first in the unitary method?
    (a) Multiply(b) Add(c) Divide(d) Subtract

C. Solve These Word Problems (Show All Steps)

  1. 7 colour pencils cost Rs 63. Find the cost of 12 colour pencils.
  2. A fruit seller in Chennai sells 5 guavas for Rs 35. Anand wants to buy 9 guavas. How much will he pay?
  3. Geeta buys 3 metres of ribbon for Rs 27. How much will 8 metres of ribbon cost?
  4. A baker in Lucknow sells 6 biscuit packets for Rs 90. What is the cost of 10 packets?
Think and Do -- Fun Activity

Market Visit: Ask a family member the price of any 3 items from a nearby shop. Write the details below and use the unitary method to find the cost of a different quantity.

ItemQuantity GivenTotal Cost (Rs)Cost of 1 Item (Rs)New QuantityNew Total Cost (Rs)