# 3rd Class Mathematics Subtraction Subtraction

Subtraction

Category : 3rd Class

LEARNING OBJECTIVES

• Understand the concept of subtraction using a 10 x 10 grid.
• Subtract using 2 digit numbers.
• Subtract using 3 digit numbers.
• Apply subtraction to real life situations.

Real life Examples

• Elevator is a real life example of addition and subtraction. The ground floor is considered to be 0.
• Subtraction helps in calculating the amount left in bank account after debits.

AMAZING FACTS

• Subtract is formed by two words “sub” and “tract”. “Sub” means “below” and “tract” means “to pull away”.
• When we subtract zero from a particular number (or digit of a number) we get the number (or the digit) itself. For example: 413-100=313

QUICK CONCEPT REVIEW

Subtraction is taking away a certain number of objects from a bigger set of objects. • Subtraction is one of the basic four operations.
• It is denoted by the symbol “-“. For example: 12 subtracted from 45 can be written as 45-12.
• The number of items left after subtraction is called “difference”.
• A 10 x 10 number grid is a helpful tool to subtract 2-digit numbers.
• Some words that denote addition are "minus", "take away" and "left",
• Addition can be done in different ways
• Counting in tens: 47- 34 = 47 - 10 -10-10-4
• Place value: 56 - 13

6 – 3 = 3

50 - 10 = 40

40 + 3 = 43

HISTORICAL PREVIESW

• The plus and minus symbols were in use before they appeared in print. For example, they were painted on barrels to indicate whether or not the barrels were full.
• To make subtraction easier it is important to regroup the numbers.

For example: 781 - 676

Subtract the ones = 11 - 6 = 5

Subtract the tens = 70-70=0

Subtract the hundreds = 700 - 600 = 100

100 + 5 = 105

MISCONCEPT/CONCEPT

• Misconcept: Subtraction is commutative.
• Concept: Subtraction is not commutative. For example:

18-13 is not equal to 13-18

PLAY TIME:

• Pick up a 3 digit number. Mix the digits of the number and form a new 3-digit number. Subtract the smaller number from the bigger number.

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