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 click on the topic to go click on the topic to go to that section to that section Table of Contents Pt. 1 Table of Contents Pt. 2 - Real World Subtraction with Manipulatives - Patterns when Subtracting 10 - Subtraction Sentences - Lab - Zero Wins - Number Stories - Fact Families - Comparing Groups - Lab - Fact Family Domino Grab - Subtraction on a Number Line - Fact Triangles - Subtraction on a Number Grid - Lab - Math Action Goes Both Ways - Subtracting Zero - Missing Number - Subtracting All - Missing Number Part 2 - Subtracting 1, 2, 3 - Get to Ten - Subtracting 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. Real World Subtraction MP4 Model with mathematics. with Manipulatives 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 Click to return to you to an example of how to meet Table of Contents this standard within the unit.
Slide 6 (Answer) / 188 Slide 7 / 188 When we subtract, we break a whole into 2 smaller parts. During this first lesson, the goal is to have students solve real life Teacher Notes number stories. By doing this, kids will make real life connections to subtraction. Before beginning the Real World Subtraction actual lesson, have the student act out subtraction stories. Ex: Joe with Manipulatives puts three crayons on the table. Two fall off. How many crayons are on the table? Have them act out at part least 4 stories. [This object is a teacher notes pull tab] 7 baseballs in the whole group Click to return to Table of Contents part Slide 7 (Answer) / 188 Slide 8 / 188 When we subtract, we break a whole How many turkeys are left? into 2 smaller parts. 4 Four turkeys are on the fence. Whole Teacher Notes Two fly away. 2 (Left) (Flew away) Teacher Notes How many turkeys left? Demonstrate moving some Part Part baseballs into each "part". part Discuss how you took the whole and broke it into 2 parts. [This object is a teacher notes pull tab] 7 baseballs in the whole group part Slide 9 / 188 Slide 10 / 188 How many potatoes are left? How many dogs are left? Jen has six potatoes on her plate. Three potatoes roll off. There are 5 dogs in the park. Teacher Notes Whole How many potatoes are left? 3 dogs ran away. Teacher Notes 6 How many dogs are left? Whole Part Part 3 (Left) (Rolled away) 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 Slide 11 (Answer) / 188 Using Counters Using Counters We can use counters to help us solve subtraction problems. We can use counters to help us solve subtraction problems. Pull down the counters Teacher Notes to represent the dogs. Continue using the counters on the new few pages. Also have students use real counters at their desks. 5 3 ________ 5 3 ________ [This object is a teacher notes pull tab] dogs ran away dogs left dogs ran away dogs left Slide 12 / 188 Slide 13 / 188 Let's Practice Let's Show it With Counters 8 2 10 5 ______ ______ apple pies balloons pies are eaten pies left blow away balloons are left Slide 14 / 188 Slide 15 / 188 Let's Practice Let's Practice 3 3 ______ 6 take away 1 _____ left leaves on a tree leaves fall off leaves left
Slide 16 / 188 Slide 17 / 188 Let's Practice Let's Practice 8 take away 3 _____ left 9 take away 5 _____ left Slide 18 / 188 Slide 18 (Answer) / 188 Connecting Cubes Connecting Cubes We can also use connecting cubes to help us subtract. We can also use connecting cubes to help us subtract. Each cube represents an object. Each cube represents an object. To show subtraction, remove the amount taken away. To show subtraction, remove the amount taken away. Pull down linking cubes Teacher Notes to represent an object. Line up the cubes so that they look like they are connected. Have students use cubes at their desks. 2 1 ________ 2 1 ________ [This object is a teacher notes pull tab] blue birds flies away birds left blue birds flies away birds left Slide 19 / 188 Slide 20 / 188 Let's Practice 1 7 dogs are outside and 3 run away. There are 10 dogs in all. Yes 5 apples 3 are rotten _____ apples left No 7 rakes 2 break _____ rakes left
Slide 20 (Answer) / 188 Slide 21 / 188 1 7 dogs are outside and 3 run away. 2 3 cats and 3 run away. _____ cats left There are 10 dogs in all. A 5 Yes B 6 No C 0 Answer No [This object is a pull tab] Slide 21 (Answer) / 188 Slide 22 / 188 2 3 cats and 3 run away. _____ cats left 3 4 rakes and 2 break. _____ rakes left A 5 A 2 B 6 B 6 C 0 C 8 Answer 0 [This object is a pull tab] Slide 22 (Answer) / 188 Slide 23 / 188 3 4 rakes and 2 break. _____ rakes left 4 3 pumpkins and 2 roll away. ____ pumpkins left A 2 B 6 Answer C 8 A [This object is a pull tab]
Slide 23 (Answer) / 188 Slide 24 / 188 5 8 hats and 3 blow away. 4 3 pumpkins and 2 roll away. ____ pumpkins left _____ hats left Answer 1 [This object is a pull tab] Slide 24 (Answer) / 188 Slide 25 / 188 5 8 hats and 3 blow away. _____ hats left Answer 5 [This object is a pull tab] Slide 26 / 188 Slide 27 / 188 Subtraction Sentences Click to return to Table of Contents
Slide 28 / 188 Slide 29 / 188 Subtraction Sentences The Minus Sign - The minus sign means to take away. 8 minus 2 equals 6 x x 1 2 3 5 6 4 Slide 30 / 188 Slide 31 / 188 Subtraction Sentence Parts Subtraction Sentence Parts A subtraction sentence has 2 parts, a minus Slide the labels to the correct part of the sign, an equal sign and a whole. subtraction sentence. Minus Sign Minus Sign Equal Sign Equal Sign 3 - 1 = 2 Whole 8 - 2 = 6 Parts Whole Parts Slide 31 (Answer) / 188 Slide 32 / 188 Subtraction Sentence Parts Subtraction Sentence Parts Slide the labels to the correct part of the Slide the labels to the correct part of the subtraction sentence. subtraction sentence. MP 6 Attend to precision Give students time to think Minus Sign Minus Sign about the different parts of a Math Practice subtraction sentence. Then Equal Sign Equal Sign call on different students to 3 - 1 = 2 9 - 4 = 5 Whole Whole come to the board to label the different parts. It is important Parts Parts for them to recognize what each part represents. [This object is a pull tab]
Slide 33 / 188 Slide 34 / 188 The Minuend The Subtrahend The first number is the largest number. The second number tell us how many we are taking It is called the minuend. away. This is called the subtrahend. 8 - 6 = 2 8 - 6 = 2 Minuend Subtrahend Slide 35 / 188 Slide 35 (Answer) / 188 The Difference The Difference The answer is called the difference. The answer is called the difference. Will the difference be greater or less than the minuend? Will the difference be greater or less than the minuend? MP 2 Reason abstractly and quantitatively. Math Practice 8 - 6 = 2 8 - 6 = 2 Ask students if the difference will be greater than or less than the minuend. Have them explain why. [This object is a pull tab] Difference Difference Slide 36 / 188 Slide 37 / 188 Left or Right Top to Bottom Subtraction sentences can be written with the Subtraction sentences can also be written top to bottom. difference on the left or right of the equal sign. 11 - 7 = 4 11 - 7 = 4 11 Difference 4 = 11 - 7 - 7 4 Difference Difference
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