LEARNING OBJECTIVES
This lesson will help you to:
- 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.
MORE ABOUT SUBRTACTION
- 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.
