Slide 1 / 188 Slide 2 / 188 First Grade Subtraction to 20 Part 1 2015-11-23 www.njctl.org Table of Contents Pt. 1 click on the topic to go to that section Slide 3 / 188 - Real World Subtraction with Manipulatives - Subtraction Sentences - Number Stories - Comparing Groups - Subtraction on a Number Line - Subtraction on a Number Grid - Subtracting Zero - Subtracting All - Subtracting 1, 2, 3 - Subtracting Ten
Table of Contents Pt. 2 click on the topic to go to that section Slide 4 / 188 - Patterns when Subtracting 10 - Lab - Zero Wins - Fact Families - Lab - Fact Family Domino Grab - Fact Triangles - Lab - Math Action Goes Both Ways - Missing Number - Missing Number Part 2 - Get to Ten - Get to Ten Part 2 Standards for Mathematical Practices Slide 5 / 188 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. MP8 Look for and express regularity in repeated reasoning. Click on each standard to bring you to an example of how to meet this standard within the unit. Slide 6 / 188 Real World Subtraction with Manipulatives Click to return to Table of Contents
When we subtract, we break a whole into 2 smaller parts. Slide 7 / 188 part 7 baseballs in the whole group part How many turkeys are left? Slide 8 / 188 Four turkeys are on the fence. 4 Whole Two fly away. How many turkeys left? 2 (Flew away) Part (Left) Part Teacher Notes How many potatoes are left? Jen has six potatoes on her plate. Slide 9 / 188 Three potatoes roll off. How many potatoes are left? 6 Whole Teacher Notes 3 (Rolled away) Part (Left) Part We could also ask, "What is the difference in the number of potatoes we started with, and the number of potatoes left?"
How many dogs are left? Slide 10 / 188 There are 5 dogs in the park. 3 dogs ran away. How many dogs are left? Part Whole Part Teacher Notes Using Counters Slide 11 / 188 We can use counters to help us solve subtraction problems. 5 3 dogs ran away dogs left Let's Show it With Counters Slide 12 / 188 8 apple pies 2 pies are eaten pies left
Let's Practice Slide 13 / 188 10 balloons 5 blow away balloons are left Let's Practice Slide 14 / 188 3 leaves on a tree 3 leaves fall off leaves left Let's Practice Slide 15 / 188 6 take away 1 left
Let's Practice Slide 16 / 188 8 take away 3 left Let's Practice Slide 17 / 188 9 take away 5 left Connecting Cubes Slide 18 / 188 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
Let's Practice Slide 19 / 188 5 apples 3 are rotten apples left 7 rakes 2 break rakes left 1 7 dogs are outside and 3 run away. There are 10 dogs in all. Slide 20 / 188 Yes No 2 3 cats and 3 run away. cats left Slide 21 / 188 A 5 B 6 C 0
3 4 rakes and 2 break. rakes left Slide 22 / 188 A 2 B 6 C 8 4 3 pumpkins and 2 roll away. Slide 23 / 188 pumpkins left 5 8 hats and 3 blow away. Slide 24 / 188 hats left
Slide 25 / 188 Slide 26 / 188 Slide 27 / 188 Subtraction Sentences Click to return to Table of Contents
Subtraction Sentences Slide 28 / 188 8 minus 2 equals 6 x 1 2 3 4 5 6 x The Minus Sign - The minus sign means to take away. Slide 29 / 188 Subtraction Sentence Parts Slide 30 / 188 A subtraction sentence has 2 parts, a minus sign, an equal sign and a whole. Minus Sign Equal Sign 8-2 = 6 Whole Parts
Subtraction Sentence Parts Slide 31 / 188 Minus Sign Slide the labels to the correct part of the subtraction sentence. Equal Sign Whole Parts 3-1 = 2 Subtraction Sentence Parts Slide 32 / 188 Minus Sign Slide the labels to the correct part of the subtraction sentence. Equal Sign Whole Parts 9-4 = 5 The Minuend Slide 33 / 188 The first number is the largest number. It is called the minuend. 8-6 = 2 Minuend
The Subtrahend Slide 34 / 188 The second number tell us how many we are taking away. This is called the subtrahend. 8-6 = 2 Subtrahend The Difference Slide 35 / 188 The answer is called the difference. Will the difference be greater or less than the minuend? 8-6 = 2 Difference Left or Right Subtraction sentences can be written with the difference on the left or right of the equal sign. 11-7 = 4 Slide 36 / 188 4 = 11-7 Difference Difference
Top to Bottom Subtraction sentences can also be written top to bottom. 11-7 = 4 11-7 4 Difference Slide 37 / 188 See, Write and Say Slide 38 / 188 See Write Say x x x 4-3 = 1 4 minus 3 equals 1 Slide 39 / 188 3 - = 1 1 2 3
9 1 Slide 40 / 188-5 2 4 3 Slide 41 / 188 6-1 = 5 1 2 3 Slide 42 / 188 2 1-2 2 0 3
Slide 43 / 188 9-3 = 6 1 2 3 Slide 44 / 188 8 1-2 2 36 Slide 45 / 188
6 Which subtraction sentence matches this story? Slide 46 / 188 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 7 Which subtraction sentence matches this story? Slide 47 / 188 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 8 Which subtraction sentence matches this story? Slide 48 / 188 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
9 Which subtraction sentence matches this story? Ten chickens are at the farm. Four fly away. How many chickens are left? Slide 49 / 188 A 10-6 = 4 B 10-4 = 6 C 10-4 = 5 10 Which subtraction sentence matches this story? Thirteen pieces of candy are on the table. Jen eats 5 pieces. There are 8 pieces left. Slide 50 / 188 A 13-8 = 5 B 13-5 = 7 C 13-5 = 8 Slide 51 / 188
Slide 52 / 188 Slide 53 / 188 Number Stories Click to return to Table of Contents Slide 54 / 188 Word Problems 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.
Slide 55 / 188 Story 1: Pennies 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 2: Cats Slide 56 / 188 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 3: People Slide 57 / 188 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.
Let's Make up a Story Slide 58 / 188 Make up a story for this number sentence. 10-7 = Let's Make up a Story Slide 59 / 188 Make up a story for this number sentence. 6-3 Class Activity Slide 60 / 188 Student made subtraction stories
11 There are 8 ants on a log. 3 crawl off. How many ants are left on the log? Slide 61 / 188 A 4 B 5 C 6 12 There are 8 ducks in the pond. 3 swim away. How many ducks are left in the pond? Slide 62 / 188 13 You have 12 pencils on your box. 6 of the pencils break. How many pencils are left in all? Slide 63 / 188 A 4 B 5 C 6
14 There are 9 hippos in a pond. 5 of them get out. How many hippos are still in the pond? Slide 64 / 188 15 You see 11 cookies in a box. Nine of them are chocolate chip. How many are not chocolate chip? Slide 65 / 188 A 4 B 2 C 3 Slide 66 / 188
Slide 67 / 188 Slide 68 / 188 Comparing Groups Click to return to Table of Contents Comparing Slide 69 / 188 How many cubes are in each train?
Comparing Slide 70 / 188 You can subtract to compare groups 6 4 Which number is more? Circle it Comparing Slide 71 / 188 We know that there are more blue blocks than green blocks. If we want to know how many more blue blocks we can subtract. 6 4 - = The bigger number is written first and then subtract the smaller number. Comparing Words Slide 72 / 188 How much less? How much shorter? How many fewer? How much smaller? How much further? How much more? How much taller? How many more? How much larger? How much closer?
Comparing Slide 73 / 188 - = 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. Slide 75 / 188
Monkeys and Zebras Slide 76 / 188 There are 8 monkeys at the zoo. There are 12 zebras at the zoo. How many more monkeys than zebras? - = Using Circles If you do not have cubes or pictures, draw circles to help. Slide 77 / 188 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 Slide 79 / 188 The worm is 6 inches. The snake is 14 inches long. How much shorter is the worm? - = 16 How many more green cubes than blue cubes? Slide 80 / 188 A 1 B 4 C 3 17 How many fewer red cubes than blue cubes? Slide 81 / 188
18 There are 10 bears. There are 2 tigers. How many more bears? Slide 82 / 188 A 12 B 8 C 10 19 8 is 5 more than 3 Slide 83 / 188 True False 20 Beth saw 4 birds. Jim saw 10 birds. How many fewer did Beth see? Slide 84 / 188
Slide 85 / 188 Slide 86 / 188 Slide 87 / 188 Subtraction on a Number Line Click to return to Table of Contents
Class Activity: Slide 88 / 188 Bead Number Line Class Activity Floor Number Line Slide 89 / 188 0 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 90 / 188 We can use a number line to find the difference between two numbers (subtract). 0 1 2 3 4 5 6 7 8 9 10 111213 1415 16171819 20 Starting number Number of jumps back 5-3 = Where did you end? 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.
Using a Number Line Slide 91 / 188 Sometimes it helps to circle the minuend to help us remember where to start. 1 2 3 Remember where to start 0 1 2 3 4 5 6 7 8 9 10 111213 1415 16171819 20 5-3 = Don't forget to start counting after you jump!! Using a Number Line Slide 92 / 188 9-4 = 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 What number should we circle? How many jumps back will we take? Where did we land? Using a Number Line Slide 93 / 188 11-8 = 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 What number should we circle? How many jumps back will we take? Where did we land?
21 6-1 = 7 Slide 94 / 188 Yes No 22 5-3 = 2 Slide 95 / 188 Yes No 23 3-3 = Slide 96 / 188 A 6 B 1 C 0
24 17-2 = Slide 97 / 188 25 16-7 = Slide 98 / 188 Slide 99 / 188
Slide 100 / 188 Slide 101 / 188 Subtraction on a Number Grid Click to return to Table of Contents Using a Number Grid Slide 102 / 188 We can use a number grid to help us subtract as well.
Using a Number Grid Slide 103 / 188 12-7 = 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. Using a Number Grid Slide 104 / 188 19-6 = Using a Number Grid Slide 105 / 188 14-3 = Look at the subtraction sentence. Where will we start on the number grid? How many jumps will we take? ** 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 = 26 11-6 = 5 Slide 110 / 188 True False 27 16-9 = Slide 111 / 188 A 6 B 2 C 7
28 17-7 = Slide 112 / 188 A 10 B 14 C 0 29 18-9 = Slide 113 / 188 30 13-8 = Slide 114 / 188 QUIZ
Slide 115 / 188 Slide 116 / 188 Slide 117 / 188 Subtracting Zero Click to return to Table of Contents
Slide 118 / 188 Amy had 8 pieces of candy. She decides to eat 0 pieces. How many pieces of candy are left? Let's work through it! Slide 119 / 188 What do we need to find out? What information do we know? How can we show this problem with counter? Slide 120 / 188 When you subtract 0, you have the same number left. 5-0 = 5
How would we show taking away zero with counters? Slide 121 / 188 6-0 = How would we show subtracting zero with cubes? Slide 122 / 188 9-0 = Remember since we are not taking away any cubes or counters, the answer is the same as the first number. Slide 123 / 188 13-0 = 13
Find the difference Slide 124 / 188 19-0 = 11-0 = 6-0 = 14-0 = 31 9-0 = 9 Slide 125 / 188 True False 32 4-0 = Slide 126 / 188 A 40 B 4 C 0
33 6-0 = Slide 127 / 188 34 10-0 = Slide 128 / 188 35 17-0 = Slide 129 / 188
Slide 130 / 188 Slide 131 / 188 Slide 132 / 188 Subtract All Click to return to Table of Contents
Class Activity: Slide 133 / 188 Simon Says When the minuend and the subtrahend are the same, you are subtracting all. Slide 134 / 188 Same 17-17 = 0 Same 9-9 = 0 When you subtract all, you have 0 left. Slide 135 / 188 xxxx 4-4 = 0 The first two numbers are the same in a subtract all problem.
How would we show taking away all with counters? Slide 136 / 188 7-7 = 8-8 = Slide 137 / 188 Cover the counters to show how many you will take away. 12-12 = Slide 138 / 188 Cover the counters to show how many you will take away.
17-17 = Slide 139 / 188 Cover the counters to show how many you will take away. 2-2 = Slide 140 / 188 Cover the counters to show how many you will take away. Let's Practice Slide 141 / 188 Use counters to demonstrate if necessary. 5-5 =
Slide 142 / 188 14-14 = Slide 143 / 188 11-11 = Slide 144 / 188 16-16 =
Sort the Subtraction Sentences Slide 145 / 188 Class Discussion Slide 146 / 188 Jen told her dad that 6-6 is a doubles fact and the answer is 12. Is Jen correct? Explain 36 12-12 = Slide 147 / 188
37 Does 9-9 = 0? Slide 148 / 188 Yes No 38 4-4 = Slide 149 / 188 39 14-14 = Slide 150 / 188 A 0 B 14 C 28
40 7-7 = Slide 151 / 188 Slide 152 / 188 Slide 153 / 188
Slide 154 / 188 Subtracting 1, 2, or 3 Click to return to Table of Contents Class Activity Slide 155 / 188 Class Activity Counting Back Songs Slide 156 / 188 10 in a Bed 10 Little Monkeys Jumping on the Bed 5 Little Ducks
Counting Backwards Slide 157 / 188 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 Try to picture a number line in your head. Find the first number, then jump back. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 4-1 = 3
Counting Backwards Slide 160 / 188 Try to picture a number line in your head. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 7-3 = What number will you start at? How many jumps will you back take? Let's Practice Slide 161 / 188 5-1 = 12-2 = 9-3 = 15-3 = 2-2 = 17-1 = Let's Practice Slide 162 / 188 We can use cubes to help us count back. To show - 1, take away one cube. 3-1 =
Let's Practice Slide 163 / 188 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 =
Class Discussion Slide 166 / 188 How can you count back to solve 15-3? 41 14-1 = Slide 167 / 188 42 17-3 = Slide 168 / 188
43 4-2 = Slide 169 / 188 44 18-2 = Slide 170 / 188 45 5-2 = Slide 171 / 188
Slide 172 / 188 Slide 173 / 188 Slide 174 / 188 Subtracting Ten Click to return to Table of Contents
Subtracting 10 Slide 175 / 188 Subtracting 10 is very easy when using a number grid. Find the minuend on the number grid and move up one box. Subtracting 10 14-10 = 4 Slide 176 / 188 Let's Practice Slide 177 / 188 16-10 =
Let's Practice Slide 178 / 188 12-10 = What number would you circle? Let's Practice Slide 179 / 188 18-10 = What number would you circle? Let's Practice Slide 180 / 188 10-10 = What number would you circle?
46 Does 15-10 = 5? Slide 181 / 188 Yes No 47 19-10 = 19 Slide 182 / 188 True False 48 18-10 = Slide 183 / 188 A 18 B 81 C 8
49 16-10 = Slide 184 / 188 50 14-10 = Slide 185 / 188 Slide 186 / 188
Slide 187 / 188 Slide 188 / 188