Real World Subtraction MP4 Model with mathematics. with - - PDF document

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First Grade

Subtraction to 20 Part 1

2015-11-23 www.njctl.org

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Table of Contents Pt. 1

• Subtraction Sentences
• Subtraction on a Number Line
• Subtraction on a Number Grid
• Number Stories
• Subtracting Zero
• Subtracting 1, 2, 3
• Subtracting Ten
• Subtracting All
• Comparing Groups
• Real World Subtraction with Manipulatives

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Table of Contents Pt. 2

• Patterns when Subtracting 10
• Fact Families
• Fact Triangles
• Missing Number Part 2
• Missing Number
• Get to Ten
• Get to Ten Part 2
• Lab - Zero Wins
• Lab - Math Action Goes Both Ways
• Lab - Fact Family Domino Grab

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Standards for Mathematical Practices

MP8 Look for and express regularity in repeated reasoning. MP1 Make sense of problems and persevere in solving them. MP2 Reason abstractly and quantitatively. MP3 Construct viable arguments and critique the reasoning of others. MP4 Model with mathematics. MP5 Use appropriate tools strategically. MP6 Attend to precision. MP7 Look for and make use of structure.

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Real World Subtraction with Manipulatives

Slide 7 / 188 When we subtract, we break a whole into 2 smaller parts.

7 baseballs in the whole group part part

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Four turkeys are on the fence. Two fly away. How many turkeys left?

4

2

How many turkeys are left?

Teacher Notes

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Jen has six potatoes on her plate. Three potatoes roll off. How many potatoes are left? We could also ask, "What is the difference in the number of potatoes we started with, and the number of potatoes left?"

6

3

How many potatoes are left?

Teacher Notes

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There are 5 dogs in the park. 3 dogs ran away. How many dogs are left?

How many dogs are left?

Teacher Notes

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5 3 ________ dogs ran away dogs left We can use counters to help us solve subtraction problems.

Using Counters Slide 12 / 188

8 apple pies 2 pies are eaten ______ pies left

Let's Show it With Counters

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10 balloons 5 blow away ______ balloons are left

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3 leaves on a tree 3 leaves fall off ______ leaves left

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6 take away 1 _____ left

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8 take away 3 _____ left

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9 take away 5 _____ left

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We can also use connecting cubes to help us subtract. Each cube represents an object. To show subtraction, remove the amount taken away. 2 1 ________ blue birds flies away birds left

Connecting Cubes

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5 apples 3 are rotten _____ apples left 7 rakes 2 break _____ rakes left

Let's Practice Slide 20 / 188 1 7 dogs are outside and 3 run away. There are 10 dogs in all. Yes No Slide 21 / 188 2 3 cats and 3 run away. _____ cats left A 5 B 6 C 0 Slide 22 / 188 3 4 rakes and 2 break. _____ rakes left A 2 B 6 C 8 Slide 23 / 188 4 3 pumpkins and 2 roll away. ____ pumpkins left Slide 24 / 188 5 8 hats and 3 blow away. _____ hats left

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Subtraction Sentences

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8 minus 2 equals 6 1 2 3 4 5 6

x x

Subtraction Sentences Slide 29 / 188

The minus sign means to take away.

• The Minus Sign

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A subtraction sentence has 2 parts, a minus sign, an equal sign and a whole.

8 - 2 = 6

Parts Minus Sign Equal Sign Whole

Subtraction Sentence Parts

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Slide the labels to the correct part of the subtraction sentence.

3 - 1 = 2

Parts Minus Sign Equal Sign Whole

Subtraction Sentence Parts Slide 32 / 188

Slide the labels to the correct part of the subtraction sentence.

9 - 4 = 5

Parts Minus Sign Equal Sign Whole

Subtraction Sentence Parts Slide 33 / 188

The first number is the largest number. It is called the minuend.

8 - 6 = 2

Minuend

The Minuend Slide 34 / 188

The second number tell us how many we are taking away. This is called the subtrahend.

8 - 6 = 2

Subtrahend

The Subtrahend Slide 35 / 188

The answer is called the difference. Will the difference be greater or less than the minuend?

8 - 6 = 2

Difference

The Difference Slide 36 / 188

Subtraction sentences can be written with the difference on the left or right of the equal sign.

11 - 7 = 4 4 = 11 - 7

Difference Difference

Left or Right

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Subtraction sentences can also be written top to bottom.

11 - 7 = 4

11

• 7

4

Difference

Top to Bottom Slide 38 / 188

See Write 4 - 3 = 1 Say

4 minus 3 equals 1

x x x

See, Write and Say Slide 39 / 188

3 - 2 = 1

1 2 3 Slide 40 / 188

9

• 5

4

1 2 3 Slide 41 / 188

6- 1 = 5

1 2 3 Slide 42 / 188

2

• 2

1 2 3

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9 - 3 = 6

1 2 3 Slide 44 / 188

8

• 2

6

3 2 1 Slide 45 / 188 Slide 46 / 188 6 Which subtraction sentence matches this story? Six kids are playing. Four kids go home. Now there are two kids left. A 6 -2 = 4 B 6 - 4 = 10 C 6 - 4 = 2 Slide 47 / 188 7 Which subtraction sentence matches this story? Five pumpkins are on the table. The farmer sells two. There are three pumpkins left. A 5 - 3 = 2 B 5 - 2 = 3 C 5 - 2 = 7 Slide 48 / 188 8 Which subtraction sentence matches this story? Six balloons are tied on the fence. Five pop. 1 balloon is left. A 6 - 5 = 1 B 6 - 1 = 5 C 6 - 5 = 2

Slide 49 / 188 9 Which subtraction sentence matches this story? Ten chickens are at the farm. Four fly away. How many chickens are left? A 10 - 6 = 4 B 10 - 4 = 6 C 10 - 4 = 5 Slide 50 / 188 10 Which subtraction sentence matches this story? Thirteen pieces of candy are on the table. Jen eats 5 pieces. There are 8 pieces left. A 13 - 8 = 5 B 13 - 5 = 7 C 13 - 5 = 8 Slide 51 / 188 Slide 52 / 188 Slide 53 / 188

Number Stories

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When looking at a subtraction word problem, we need to figure out if the numbers we know show the whole number of things or the parts.

Word Problems

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Jim has 8 pennies. His mom takes 2 away. How many pennies does Jim have left? Underline what we know. Circle what we want to know.

=

• Story 1: Pennies

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There are 5 cats on the fence. 1 jumps down. How many cats are left on the fence? Underline what we know. Circle what we want to know.

=

• Story 2: Cats

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There are 4 people at the farm. 2 people leave the farm. How many people are left at the farm? Underline what we know. Circle what we want to know.

=

• Story 3: People

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10 - 7 =

Make up a story for this number sentence.

Let's Make up a Story Slide 59 / 188

6

• 3

Make up a story for this number sentence.

Let's Make up a Story Slide 60 / 188 Class Activity

Student made subtraction stories

Slide 61 / 188 11 There are 8 ants on a log. 3 crawl off. How many ants are left on the log? A 4 B 5 C 6 Slide 62 / 188 12 There are 8 ducks in the pond. 3 swim away. How many ducks are left in the pond? Slide 63 / 188 13 You have 12 pencils on your box. 6 of the pencils break. How many pencils are left in all? A 4 B 5 C 6 Slide 64 / 188 14 There are 9 hippos in a pond. 5 of them get out. How many hippos are still in the pond? Slide 65 / 188 15 You see 11 cookies in a box. Nine of them are chocolate chip. How many are not chocolate chip? A 4 B 2 C 3 Slide 66 / 188

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Comparing Groups

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How many cubes are in each train? ______ ______

Comparing Slide 70 / 188

6 4 Which number is more? Circle it You can subtract to compare groups

Comparing Slide 71 / 188

6 4 ______ - ______ = ______ We know that there are more blue blocks than green

• blocks. If we want to know how many more blue blocks

we can subtract. The bigger number is written first and then subtract the smaller number.

Comparing Slide 72 / 188

How much less? How much more? How much shorter? How much taller? How many fewer? How many more? How much smaller? How much larger? How much further? How much closer?

Comparing Words

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______ - ______ = ______ The bigger number is written first and then subtract the smaller number. ______ ______

Comparing Slide 74 / 188

______ - ______ = ______ The bigger number is written first and then subtract the smaller number. ______ ______

Comparing Slide 75 / 188 Slide 76 / 188

There are 8 monkeys at the zoo. There are 12 zebras at the zoo. How many more monkeys than zebras? ______ - ______ = ______

Monkeys and Zebras Slide 77 / 188

If you do not have cubes or pictures, draw circles to help. There are 6 elephants. There are 2 lions. How many fewer lions? E L ______ - ______ = ______ Draw a line to see what is left behind.

Using Circles Slide 78 / 188

If you do not have cubes or pictures, draw circles to help. There are 10 tigers. There are 6 cheetahs. How many more tigers? ______ - ______ = ______ Draw a line to see what is left behind.

Using Circles

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The worm is 6 inches. The snake is 14 inches long. How much shorter is the worm? ______ - ______ = ______

Using Circles Slide 80 / 188 16 How many more green cubes than blue cubes? A 1 B 4 C 3 Slide 81 / 188 17 How many fewer red cubes than blue cubes? Slide 82 / 188 18 There are 10 bears. There are 2

• tigers. How many more bears?

A 12 B 8 C 10 Slide 83 / 188 19 8 is 5 more than 3 True False Slide 84 / 188 20 Beth saw 4 birds. Jim saw 10 birds. How many fewer did Beth see?

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Subtraction on a Number Line

Slide 88 / 188 Class Activity: Bead Number Line Slide 89 / 188 Class Activity Floor Number Line

=

• 1

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

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We can use a number line to find the difference between two numbers (subtract). 5 - 3 = _____ The minuend tells us where to start. The subtrahend tells us how many jumps to take back. The difference (answer) of the two numbers is where we end.

1 2 3 4 5 6 7 8 9 10 111213 1415 16171819 20

Using a Number Line

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Sometimes it helps to circle the minuend to help us remember where to start.

5 - 3 = _____

Don't forget to start counting after you jump!! 1 2 3 1 2 3 4 5 6 7 8 9 10 111213 1415 16171819 20 Remember where to start

Using a Number Line Slide 92 / 188 9 - 4 = _____

What number should we circle? How many jumps back will we take? Where did we land?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Using a Number Line Slide 93 / 188

What number should we circle? How many jumps back will we take? Where did we land?

11 - 8 = _____

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Using a Number Line Slide 94 / 188 21 6 - 1 = 7 Yes No Slide 95 / 188 22 5 - 3 = 2 Yes No Slide 96 / 188 23 3 - 3 = ____ A 6 B 1 C 0

Slide 97 / 188 24 17 - 2 = _____ Slide 98 / 188 25 16 - 7 = _____ Slide 99 / 188 Slide 100 / 188 Slide 101 / 188

Subtraction on a Number Grid

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We can use a number grid to help us subtract as well.

Using a Number Grid

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The minuend tells us where to start. The subtrahend tells us how many jumps to take back. The difference between the two numbers (answer) is where we end.

12 - 7 = ____ Using a Number Grid Slide 104 / 188 19 - 6 = ____ Using a Number Grid Slide 105 / 188

Look at the subtraction sentence. Where will we start on the number grid? How many jumps will we take?

14 - 3 = ____

** Just like on a number line, don't count until you jump **

Using a Number Grid Slide 106 / 188 14 - 4 = ____

What should we do when we get to the last number in a row?

Using a Number Grid Slide 107 / 188 17 - 8 = ____ Using a Number Grid Slide 108 / 188 20 - 5 = ____ Using a Number Grid

Slide 109 / 188 7 - 6 = ____ Using a Number Grid Slide 110 / 188 26 11 - 6 = 5 True False Slide 111 / 188 27 16 - 9 = _____ A 6 B 2 C 7 Slide 112 / 188 28 17 - 7 = _____ A 10 B 14 C 0 Slide 113 / 188 29 18 - 9 = _____ Slide 114 / 188 30 13 - 8 = _____

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Subtracting Zero

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Amy had 8 pieces of candy. She decides to eat 0 pieces. How many pieces of candy are left?

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What do we need to find out? What information do we know? How can we show this problem with counter?

Let's work through it! Slide 120 / 188

When you subtract 0, you have the same number left.

5 - 0 = 5

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How would we show taking away zero with counters?

6 - 0 =

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How would we show subtracting zero with cubes?

9 - 0 =

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Remember since we are not taking away any cubes or counters, the answer is the same as the first number.

13 - 0 = 13

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19 - 0 = ______ 11 - 0 = ______ 6 - 0 = ______ 14 - 0 = ______

Find the difference Slide 125 / 188 31 9 - 0 = 9 True False Slide 126 / 188 32 4 - 0 = ______ A 40 B 4 C 0

Slide 127 / 188 33 6 - 0 = ____ Slide 128 / 188 34 10 - 0 = _____ Slide 129 / 188 35 17 - 0 = _____ Slide 130 / 188 Slide 131 / 188 Slide 132 / 188

Subtract All

Slide 133 / 188 Class Activity: Simon Says Slide 134 / 188

When the minuend and the subtrahend are the same, you are subtracting all.

17 - 17 = 0

Same

9 - 9 = 0

Same

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When you subtract all, you have 0 left.

xxxx

4 - 4 = 0

The first two numbers are the same in a subtract all problem.

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How would we show taking away all with counters?

7 - 7 =

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8 - 8 = _____

Cover the counters to show how many you will take away.

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12 - 12 = ___

Cover the counters to show how many you will take away.

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17 - 17 = ___

Cover the counters to show how many you will take away.

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2 - 2 = ___

Cover the counters to show how many you will take away.

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5 - 5 = ___

Use counters to demonstrate if necessary.

Let's Practice Slide 142 / 188

14 - 14 = ____

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11 - 11 = ____

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16 - 16 = ____

Slide 145 / 188 Sort the Subtraction Sentences Slide 146 / 188 Class Discussion

Jen told her dad that 6 - 6 is a doubles fact and the answer is 12. Is Jen correct? Explain

Slide 147 / 188 36 12 - 12 = _____ Slide 148 / 188 37 Does 9 - 9 = 0? Yes No Slide 149 / 188 38 4 - 4 = _____ Slide 150 / 188 39 14 - 14 = A 0 B 14 C 28

Slide 151 / 188 40 7 - 7 = _____ Slide 152 / 188 Slide 153 / 188 Slide 154 / 188

Subtracting 1, 2, or 3

Slide 155 / 188 Class Activity Slide 156 / 188 Class Activity Counting Back Songs

10 in a Bed 10 Little Monkeys Jumping on the Bed 5 Little Ducks

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Counting backwards can help us subtract.

8 - 3 = 5

7 6 5

Counting Backwards Slide 158 / 188

Counting backwards can help us subtract.

6 - 2 = 4

5 4

Counting Backwards Slide 159 / 188

4 - 1 = 3

Try to picture a number line in your head. Find the first number, then jump back.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Counting Backwards Slide 160 / 188

Try to picture a number line in your head.

7 - 3 = __

What number will you start at? How many jumps will you back take?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Counting Backwards Slide 161 / 188 5 - 1 = _____ 12 - 2 = _____ Let's Practice 9 - 3 = _____ 15 - 3 = _____ 2 - 2 = _____ 17 - 1 = _____ Slide 162 / 188

We can use cubes to help us count back. To show - 1, take away one cube. 3 - 1 =

Let's Practice

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Your mom gave you five cookies. Then she took two away. How many are left?

5 - 2 = Let's Practice Slide 164 / 188

You picked 9 flowers. You gave one away. How many are left?

9 - 1 = Let's Practice Slide 165 / 188

Your sister has 12 crayons. She gave 3 away. How many are left?

12 - 3 = Let's Practice Slide 166 / 188 Class Discussion

How can you count back to solve 15 - 3?

Slide 167 / 188 41 14 - 1 = Slide 168 / 188 42 17 - 3 =

Slide 169 / 188 43 4 - 2 = Slide 170 / 188 44 18 - 2 = Slide 171 / 188 45 5 - 2 = Slide 172 / 188 Slide 173 / 188 Slide 174 / 188

Subtracting Ten

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Subtracting 10 is very easy when using a number grid. Find the minuend on the number grid and move up one box.

Subtracting 10 Slide 176 / 188

14 - 10 = 4

Subtracting 10 Slide 177 / 188

16 - 10 =

Let's Practice Slide 178 / 188

12 - 10 =

Let's Practice

What number would you circle?

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18 - 10 =

Let's Practice

What number would you circle?

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10 - 10 =

Let's Practice

What number would you circle?

Slide 181 / 188 46 Does 15 - 10 = 5 ? Yes No Slide 182 / 188 47 19 - 10 = 19 True False Slide 183 / 188 48 18 - 10 = A 18 B 81 C 8 Slide 184 / 188 49 16 - 10 = Slide 185 / 188 50 14 - 10 = Slide 186 / 188

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