Slide 1 / 188 Slide 2 / 188 First Grade Subtraction to 20 Part 1 2015-11-23 www.njctl.org Slide 3 / 188 Slide 4 / 188 Table of Contents Pt. 1 click on the topic to go to that section Table of Contents Pt. 2 click on the topic to go to that section - 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 - 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 Slide 5 / 188 Slide 6 / 188 Standards for Mathematical Practices 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. Real World Subtraction with Manipulatives 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. Click to return to Table of Contents
Slide 7 / 188 When we subtract, we break a whole into 2 smaller parts. Slide 8 / 188 How many turkeys are left? Four turkeys are on the fence. 4 Whole part Two fly away. How many turkeys left? 2 (Flew away) Part (Left) Part Teacher Notes 7 baseballs in the whole group part Slide 9 / 188 How many potatoes are left? Jen has six potatoes on her plate. Slide 10 / 188 How many dogs are left? Three potatoes roll off. There are 5 dogs in the park. How many potatoes are left? 3 6 Whole Teacher Notes 3 dogs ran away. How many dogs are left? Part Whole Part Teacher Notes (Rolled away) (Left) Part Part We could also ask, "What is the difference in the number of potatoes we started with, and the number of potatoes left?" Slide 11 / 188 Using Counters Slide 12 / 188 Let's Show it With Counters We can use counters to help us solve subtraction problems. 5 3 dogs ran away dogs left 8 apple pies 2 pies are eaten pies left
Slide 13 / 188 Let's Practice Slide 14 / 188 Let's Practice 10 balloons 5 blow away balloons are left 3 leaves on a tree 3 leaves fall off leaves left Slide 15 / 188 Let's Practice Slide 16 / 188 Let's Practice 6 take away 1 left 8 take away 3 left Slide 17 / 188 Let's Practice Slide 18 / 188 Connecting Cubes We can also use connecting cubes to help us subtract. Each cube represents an object. To show subtraction, remove the amount taken away. 9 take away 5 left 2 1 blue birds flies away birds left
Slide 19 / 188 Let's Practice 5 apples 3 are rotten apples left Slide 20 / 188 1 7 dogs are outside and 3 run away. There are 10 dogs in all. Yes No 7 rakes 2 break rakes left 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
Slide 25 / 188 Slide 26 / 188 Slide 27 / 188 Slide 28 / 188 Subtraction Sentences Subtraction Sentences 8 minus 2 equals 6 x 1 2 3 4 5 6 x Click to return to Table of Contents Slide 29 / 188 The Minus Sign - The minus sign means to take away. Slide 30 / 188 Subtraction Sentence Parts A subtraction sentence has 2 parts, a minus sign, an equal sign and a whole. Minus Sign 8-2 = 6 Whole Parts Equal Sign
Minus Sign Slide 31 / 188 Subtraction Sentence Parts Slide the labels to the correct part of the subtraction sentence. Minus Sign Slide 32 / 188 Subtraction Sentence Parts Slide the labels to the correct part of the subtraction sentence. Equal Sign Whole Parts 3-1 = 2 Equal Sign Whole Parts 9-4 = 5 Slide 33 / 188 Slide 34 / 188 The Minuend The Subtrahend The first number is the largest number. It is called the minuend. 8-6 = 2 The second number tell us how many we are taking away. This is called the subtrahend. 8-6 = 2 Minuend Subtrahend Slide 35 / 188 The Difference The answer is called the difference. Will the difference be greater or less than the minuend? 8-6 = 2 Difference Slide 36 / 188 Left or Right 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
Slide 37 / 188 Top to Bottom Subtraction sentences can also be written top to bottom. 11-7 = 4 11-7 4 Difference Slide 39 / 188 3 - = 1 1 2 3 See Write Say Slide 38 / 188 See, Write and Say x x x 4-3 = 1 4 minus 3 equals 1 Slide 40 / 188 9 1-5 2 4 3 Slide 41 / 188 Slide 42 / 188 6-1 = 5 1 2 3 2 1-2 2 0 3
Slide 43 / 188 Slide 44 / 188 8 1 9-3 = 6 1 2 3-2 2 36 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 Slide 54 / 188 Word Problems Number Stories 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. Click to return to Table of Contents
Slide 55 / 188 Jim has 8 pennies. His mom takes 2 away. How many pennies does Jim have left? - Story 1: Pennies Underline what we know. Circle what we want to know. = Slide 57 / 188 There are 4 people at the farm. 2 people leave the farm. How many people are left at the farm? - Story 3: People Underline what we know. Circle what we want to know. = Slide 59 / 188 Let's Make up a Story Slide 56 / 188 There are 5 cats on the fence. 1 jumps down. How many cats are left on the fence? - Story 2: Cats Underline what we know. Circle what we want to know. = Slide 58 / 188 Let's Make up a Story Make up a story for this number sentence. 10-7 = Slide 60 / 188 Class Activity Make up a story for this number sentence. 6 Student made subtraction stories - 3
Slide 61 / 188 11 There are 8 ants on a log. 3 crawl off. How many ants are left on the log? Slide 62 / 188 12 There are 8 ducks in the pond. 3 swim away. How many ducks are left in the pond? A 4 B 5 C 6 Slide 63 / 188 13 You have 12 pencils on your box. 6 of the pencils break. How many pencils are left in all? Slide 64 / 188 14 There are 9 hippos in a pond. 5 of them get out. How many hippos are still in the pond? A 4 B 5 C 6 Slide 65 / 188 Slide 66 / 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 67 / 188 Slide 68 / 188 Comparing Groups Click to return to Table of Contents Slide 69 / 188 Comparing How many cubes are in each train? Slide 70 / 188 Comparing You can subtract to compare groups 6 4 Which number is more? Circle it Slide 71 / 188 Comparing We know that there are more blue blocks than green blocks. If we want to know how many more blue blocks we can subtract. Slide 72 / 188 Comparing Words 6 4 - = The bigger number is written first and then subtract the smaller number. 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?
Slide 73 / 188 Comparing Slide 74 / 188 Comparing - = - = The bigger number is written first and then subtract the smaller number. The bigger number is written first and then subtract the smaller number. Slide 75 / 188 Slide 76 / 188 Monkeys and Zebras There are 8 monkeys at the zoo. There are 12 zebras at the zoo. How many more monkeys than zebras? - = Slide 77 / 188 If you do not have cubes or pictures, draw circles to help. E L Using Circles There are 6 elephants. There are 2 lions. How many fewer lions? - = Draw a line to see what is left behind. Slide 78 / 188 Using Circles 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.
Slide 79 / 188 Using Circles The worm is 6 inches. The snake is 14 inches long. How much shorter is the worm? 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?
Slide 85 / 188 Slide 86 / 188 Slide 87 / 188 Slide 88 / 188 Class Activity: Bead Number Line Subtraction on a Number Line Click to return to Table of Contents Slide 89 / 188 Class Activity Floor Number Line 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Slide 90 / 188 Using a Number Line 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.
Slide 91 / 188 Sometimes it helps to circle the minuend to help us remember where to start. 1 2 3 Using a Number Line Remember where to start 0 1 2 3 4 5 6 7 8 9 10 111213 1415 16171819 20 5-3 = Slide 92 / 188 Using a Number Line 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? Don't forget to start counting after you jump!! Slide 93 / 188 Slide 94 / 188 Using a Number Line 11-8 = 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 6-1 = 7 Yes No What number should we circle? How many jumps back will we take? Where did we land? Slide 95 / 188 Slide 96 / 188 22 5-3 = 2 Yes No 23 3-3 = 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 Slide 102 / 188 Using a Number Grid Subtraction on a Number Grid We can use a number grid to help us subtract as well. Click to return to Table of Contents
Slide 103 / 188 Using a Number Grid Slide 104 / 188 Using a Number Grid 12-7 = 19-6 = 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. Slide 105 / 188 Using a Number Grid Slide 106 / 188 Using a Number Grid 14-3 = 14-4 = 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 ** Slide 107 / 188 Using a Number Grid What should we do when we get to the last number in a row? Slide 108 / 188 Using a Number Grid 17-8 = 20-5 =
Slide 109 / 188 Slide 110 / 188 Using a Number Grid 26 11-6 = 5 True 7-6 = 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 29 18-9 = Slide 113 / 188 30 13-8 = Slide 114 / 188 QUIZ
Slide 115 / 188 Slide 116 / 188 Slide 117 / 188 Slide 118 / 188 Amy had 8 pieces of candy. She decides to eat 0 pieces. How many pieces of candy are left? Subtracting Zero Click to return to Table of Contents Slide 119 / 188 Slide 120 / 188 Let's work through it! When you subtract 0, you have the same number left. What do we need to find out? What information do we know? How can we show this problem with counter? 5-0 = 5
Slide 121 / 188 Slide 122 / 188 How would we show taking away zero with counters? How would we show subtracting zero with cubes? 6-0 = 9-0 = Slide 123 / 188 Remember since we are not taking away any cubes or counters, the answer is the same as the first number. 13-0 = 13 Slide 124 / 188 Find the difference 19-0 = 11-0 = 6-0 = 14-0 = Slide 125 / 188 Slide 126 / 188 31 9-0 = 9 True False 32 4-0 = A 40 B 4 C 0
33 6-0 = Slide 127 / 188 34 10-0 = Slide 128 / 188 Slide 129 / 188 Slide 130 / 188 35 17-0 = Slide 131 / 188 Slide 132 / 188 Subtract All Click to return to Table of Contents
Slide 133 / 188 Class Activity: Simon Says Slide 134 / 188 When the minuend and the subtrahend are the same, you are subtracting all. Same 17-17 = 0 Same 9-9 = 0 Slide 135 / 188 Slide 136 / 188 When you subtract all, you have 0 left. How would we show taking away all with counters? xxxx 4-4 = 0 The first two numbers are the same in a subtract all problem. Slide 137 / 188 8-8 = 7-7 = Slide 138 / 188 12-12 = Cover the counters to show how many you will take away. Cover the counters to show how many you will take away.
Slide 139 / 188 17-17 = Slide 140 / 188 2-2 = Cover the counters to show how many you will take away. Cover the counters to show how many you will take away. Slide 141 / 188 Slide 142 / 188 Let's Practice Use counters to demonstrate if necessary. 5-5 = 14-14 = Slide 143 / 188 Slide 144 / 188 11-11 = 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 36 12-12 = Slide 147 / 188 37 Does 9-9 = 0? Slide 148 / 188 Yes No Slide 149 / 188 Slide 150 / 188 38 4-4 = 39 14-14 = A 0 B 14 C 28
Slide 151 / 188 Slide 152 / 188 40 7-7 = Slide 153 / 188 Slide 154 / 188 Subtracting 1, 2, or 3 Click to return to Table of Contents 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
Slide 157 / 188 Counting Backwards Counting backwards can help us subtract. Slide 158 / 188 Counting Backwards Counting backwards can help us subtract. 8-3 = 5 7 6 5 6-2 = 4 5 4 Slide 159 / 188 Counting Backwards Try to picture a number line in your head. Find the first number, then jump back. Slide 160 / 188 Counting Backwards 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 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 4-1 = 3 Slide 161 / 188 Let's Practice 5-1 = 12-2 = 7-3 = What number will you start at? How many jumps will you back take? Slide 162 / 188 Let's Practice We can use cubes to help us count back. To show - 1, take away one cube. 3-1 = 9-3 = 15-3 = 2-2 = 17-1 =
Slide 163 / 188 Let's Practice Your mom gave you five cookies. Then she took two away. How many are left? 5-2 = Slide 164 / 188 Let's Practice You picked 9 flowers. You gave one away. How many are left? 9-1 = Slide 165 / 188 Let's Practice Slide 166 / 188 Class Discussion Your sister has 12 crayons. She gave 3 away. How many are left? 12-3 = How can you count back to solve 15-3? Slide 167 / 188 Slide 168 / 188 41 14-1 = 42 17-3 =
Slide 169 / 188 Slide 170 / 188 43 4-2 = 44 18-2 = Slide 171 / 188 Slide 172 / 188 45 5-2 = Slide 173 / 188 Slide 174 / 188 Subtracting Ten Click to return to Table of Contents
Slide 175 / 188 Subtracting 10 Subtracting 10 is very easy when using a number grid. Slide 176 / 188 Subtracting 10 14-10 = 4 Find the minuend on the number grid and move up one box. Slide 177 / 188 Let's Practice Slide 178 / 188 Let's Practice 16-10 = 12-10 = What number would you circle? Slide 179 / 188 Let's Practice 18-10 = Slide 180 / 188 Let's Practice 10-10 = What number would you circle? What number would you circle?
Slide 181 / 188 Slide 182 / 188 46 Does 15-10 = 5? Yes No 47 19-10 = 19 True False Slide 183 / 188 Slide 184 / 188 48 18-10 = 49 16-10 = A 18 B 81 C 8 Slide 185 / 188 Slide 186 / 188 50 14-10 =
Slide 187 / 188 Slide 188 / 188