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- Fourth Class Maths
- Adding and Subtracting Numbers

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Get Started Now- Intro Lesson: a6:34
- Intro Lesson: b6:35
- Intro Lesson: c7:29
- Intro Lesson: d4:06
- Lesson: 1a3:07
- Lesson: 1b2:52
- Lesson: 1c2:46
- Lesson: 1d3:47
- Lesson: 2a1:33
- Lesson: 2b1:38
- Lesson: 2c1:28
- Lesson: 3a1:53
- Lesson: 3b2:08
- Lesson: 3c2:00
- Lesson: 4a2:47
- Lesson: 4b2:39
- Lesson: 4c2:43
- Lesson: 5a3:31
- Lesson: 5b3:07
- Lesson: 5c3:54
- Lesson: 6a3:59
- Lesson: 6b5:14
- Lesson: 6c4:05

In this lesson, we will learn:

- The subtraction strategy of: (1) using a friendly number with adjustment, (2) adding to both numbers to create a friendly number, and (3) counting on from the first number (subtrahend)
- Understanding subtracting by 9

- Method 1: change into a "
**friendly**" number then**adjust**(by adding) __Round__one the number being taken away to the nearest multiple of 10- Then
__adjust__by adding how much you rounded by to get the answer

- Method 2: make "
**friendly**" numbers by adding to**both**numbers __Add__to one of the numbers so that it becomes the nearest multiple of 10__Add__the same amount to the other number

- Method 3: subtracting by counting on
- Start with the number you're taking away (the second number)
- Then count up until you get the first number

- IntroductionIntroduction to Subtraction Strategies:a)Mental math and differences of 10b)Subtraction strategy #1: friendly number with adjustmentc)Subtraction strategy #2: friendly number by adding to both numbersd)Subtraction strategy #3: counting on from the first number
- 1.
**Subtracting by breaking up the subtrahend**

Subtract by breaking up the number being taken away.

Fill in the blanks by following the example:

a)57 - 9 = 57 - 7 - ____ = 50 - ____ = ____b)64 - 7 = 64 - ____ - ____ = 60 - ____ = ____c)38 - 9 = 38 - ____ - ____ = 30 - ____ = ____d)92 - 8 = 92 - ____ - ____ = ____ - _____ = _____ - 2.
**Subtracting by 9 strategy**

Subtract 9 by: subtracting 10 first, then putting 1 backa)17 - 9 = ____

17 - 10 = ____ + 1 = ____b)42 - 9 = ____

42 - 10 = ____ + 1 = ____c)35 - 9 = ____

35 - 10 = ____ + 1 = ____ - 3.
**Subtracting by 8 strategy**

Subtract 8 by: subtracting 10 first, then putting 2 backa)15 - 8 = ____

15 - 10 = ____ + 2 = ____b)63 - 8 = ____

63 - 10 = ____ + 2 = ____c)47 - 8 = ____

47 - 10 = ____ + 2 = ____ - 4.
**Subtracting using friendly numbers with adjustment**

Subtract by changing one number into a "friendly" number and adjust. Fill in the blanks.a)b)c) - 5.
**Subtraction strategy: make friendly numbers by adding to both numbers**

Subtract: make "friendly" numbers by adding to both numbers. Fill in the blanks.a)b)c) - 6.
**Subtraction strategy: counting on from the second number**

Subtract by counting on from the second number. Show your work.a)573 - 252 = ____b)408 - 126 = ____c)847 - 639 = ____