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Slide 2 / 225 1st Grade Two Digit Subtraction 2015-11-30 www.njctl.org
Slide 3 / 225 Table of Contents - Subtracting Ten from Multiples of Ten with Blocks - Subtracting Ten from Multiples of Ten in Our Head - Subtracting Ten with Blocks - Subtracting Ten on a Number Grid - Subtracting Ten Patterns - Subtracting Multiples of Ten with Blocks - Subtracting Multiples of Ten on a Number Grid - Patterns When Subtracting Multiples of Ten - Lab: Subtraction Dice Roll - Two Digit Minus One Digit - Two Digit Minus Two Digit - Two Digit Minus Two Digit Pt. 2 - Lab: Subtraction Spin - Word Problems - Lab: Subtraction Around the Room - Extra Word Problems (If needed) click on the topic to go to that section
Slide 4 / 225 Standards for Mathematical Practices MP 1 Make sense of problems and persevere in solving them. MP 2 Reason abstractly and quantitatively. MP 3 Construct viable arguments and critique the reasoning of others. MP 4 Model with mathematics. MP 5 Use appropriate tools strategically. MP 6 Attend to precision. MP 7 Look for and make use of structure. MP 8 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 5 / 225 Subtracting 10 from Multiples of 10 with Blocks Click to return to Table of Contents
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Slide 16 / 225 Class Discussion How is subtracting 6-1 similar to 60-10?
Slide 17 / 225 1 The base ten blocks show 20-10 = 10 True False
Slide 18 / 225 2 60-10 = A 5 B 50 C 70
Slide 19 / 225 3 8 tens - 1 ten = tens
Slide 20 / 225 4 Which block should we use to show 50-10 = A 40 B cube C long
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Slide 24 / 225 Subtracting Ten From Multiples of Ten in Our Heads Click to return to Table of Contents
Slide 25 / 225 Let's Count By Tens 10 20 30 40 50 60 70 80 90 100 Now let's write them backwards starting with 100! 100,,,,,,,,,
Slide 26 / 225 Let's Count Back By Tens. Start 100! 100 90 80 70 60 50 40 30 20 10 Now let's write them forwards starting with 10! 10,,,,,,,,,
Slide 27 / 225 Patterns when Counting 100, 90, 80, 70, 60, 50, 40, 30, 20, 10 What pattern do you see 100, 90, when 80, 70, counting 60, backwards? 50, 40, 30, 20, 10
Slide 28 / 225 Practice 50, 40, 30,, 90, 80, 70,, 80, 70, 60,, 100, 90, 80,, 60, 50, 40,,
Slide 29 / 225 Subtracting When subtracting ten, the tens place goes down by 1. 50-10 = 40 70-10 = 60
Slide 30 / 225 Practice 80-10 =
Slide 31 / 225 Practice 40-10 =
Slide 32 / 225 Practice 60-10 =
Slide 33 / 225 6 30-10 = A 40 B 20 C 30
Slide 34 / 225 7 10-10 = A 20 B 0 C 10
Slide 35 / 225 8 70-10 = A 60 B 80 C 10
9 90-10 = Slide 36 / 225
10 20-10 = Slide 37 / 225
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Slide 40 / 225 Subtracting 10 with Blocks Click to return to Table of Contents
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Slide 48 / 225 11 34-10 = 24 Yes No ** Use blocks at your desk to help you **
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Slide 52 / 225 15 82-10 = ** Use blocks at your desk to help you **
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Slide 55 / 225 Subtracting Ten on a Number Grid Click to return to Table of Contents
Slide 56 / 225 Number Grid Subtracting 10 is very easy when using a number grid. Find the number you are subtracting 10 from on the number grid and circle it. Then move up one box.
Slide 57 / 225 24-10 = 14
Slide 58 / 225 40-10 = 30 Find the first number on the number grid. Since we are subtracting from a multiple of 10, the number will always be in the last row. Then, move up one jump.
Slide 59 / 225 Let's try another one 56-10 = First, find the number on the number grid. Then jump up one.
Slide 60 / 225 Let's try another one 34-10 = What number should we circle?
Slide 61 / 225 Let's try another one 63-10 = What number should we circle?
Slide 62 / 225 Let's try another one 19-10 =
Slide 63 / 225 Let's try another one 80-10 =
Slide 64 / 225 Class Discussion John used his number grid to help solve the subtraction sentence below. He said the answer is 25. Is he correct? What did he do wrong? 24-10 =
Slide 65 / 225 16 25-10 = 24 Yes No
Slide 66 / 225 17 39-10 = 49 True False
Slide 67 / 225 18 58-10 = A 68 B 48 C 58
19 34-10 = Slide 68 / 225
20 74-10 = Slide 69 / 225
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Slide 72 / 225 Subtracting 10 Patterns Click to return to Table of Contents
Slide 73 / 225 Tens Ones 46-10 When subtracting 10, the tens place always goes down 1 and the ones place stays the same. 36
Slide 74 / 225 62-10 52 39-10 29 24-10 14 77-10 67
Slide 75 / 225 2 3-1 0 6 4-1 0 5 6-1 0 3 7-1 0
Slide 76 / 225 Let's Practice 65-10 = 85-10 = 38-10 = 61-10 =
Slide 77 / 225 Web Practice Click here for a game. Select level 3
Slide 78 / 225 21 59-10 = 69 True False
Slide 79 / 225 22 67-10 = A 57 B 77 C 66
Slide 80 / 225 23 31-10 = A 41 B 21 C 30
24 45-10 = Slide 81 / 225
25 32-10 = Slide 82 / 225
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Slide 85 / 225 Subtracting Multiples of 10 with Blocks Click to return to Table of Contents
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Slide 92 / 225 26 Does 40-20 = 10? Yes No ** Use your blocks to help you **
Slide 93 / 225 27 80-70 = 10 True False ** Use your blocks to help you **
Slide 94 / 225 28 40-30 = A 20 B 70 C 10 ** Use your blocks to help you **
Slide 95 / 225 29 90-60 = ** Use your blocks to help you **
Slide 96 / 225 30 50-50 = ** Use your blocks to help you **
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Slide 99 / 225 Subtracting Multiples of Ten on a Number Grid Click to return to Table of Contents
Slide 100 / 225 Count by 10's Let's warm up our brains by skip counting by 10's using different voices. Can you count by 10s in a: - scary voice? - mommy voice? - baby voice? - daddy voice? 10, 20, 30
Slide 101 / 225 Subtract To subtract multiples of 10 on a number grid, you count by 10s. 40 30 20 10 60-40 = Find the first number on the grid and circle it. Count by 10s and move up one jump for each number you say. Stop when you say the second number in the subtraction sentence. The number you land on is the answer.
Slide 102 / 225 Subtract Count by 10 as you move up to solve the subtraction sentence. 80-20 = What number should you circle?
Slide 103 / 225 Subtract Count by 10 as you move up to solve the subtraction sentence. 30-10 = What number should you circle?
Slide 104 / 225 Subtract Count by 10 as you move up to solve the subtraction sentence. 70-50 = What number should you circle?
Slide 105 / 225 Subtract 90-20 =
Slide 106 / 225 Subtract 50-40 =
Slide 107 / 225 31 60-20 = A 80 B 50 C 40 ** Use your number grid to help you **
Slide 108 / 225 32 When subtracting multiples of 10, we need to count by. A 1 B 5 C 10
Slide 109 / 225 33 90-40 = A 40 B 50 C 60 ** Use your number grid to help you **
Slide 110 / 225 34 50-30 = ** Use your number grid to help you **
Slide 111 / 225 35 20-10 = ** Use your number grid to help you **
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Slide 114 / 225 Patterns When Subtracting Multiples of Ten Click to return to Table of Contents
Slide 115 / 225 Let's Count By 10s What digit changes when we count by 10s?
Slide 116 / 225 What number is this? Take 20 away and what number does it become? What digit changed?
Slide 117 / 225 30-20 = 10
Slide 118 / 225 What number is this? Take 40 away and what number does it become? What digit changed?
Slide 119 / 225 What number is this? Take ten away and what number does it become? What digit changed?
Slide 120 / 225 Count back by 10s 60, 50,,,, 70, 60,,,, 40, 30,,,, 60, 50,,,,
Slide 121 / 225 What number is 20 less? 40 30 60 20 80 70
Slide 122 / 225 36 10 less than 50 is 5? True False
Slide 123 / 225 37 20 less than 90 is 80? Yes No
Slide 124 / 225 38 What is 30 less than 40?
Slide 125 / 225 39 What is 40 less than 50?
Slide 126 / 225 40 70-40 =? QUIZ
Slide 127 / 225 Lab: Subtracting 10 Dice Roll Directions: Split students into groups of 2 and give each group 2 dice Each student rolls 1 dice and they work together to build the largest two digit number with their dice Students write the number in the box on their worksheet Students subtract 10 and write the answer on the line Click here for more information. Click to return to Table of Contents
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Slide 130 / 225 Two Digit Minus One Digit Click to return to Table of Contents
Slide 131 / 225 Subtracting When subtracting a 1 digit number from a 2 digit number, it is very important to line them up on top of each other. 36-2 All of the numbers should be on the right
Slide 132 / 225 Subtracting Can you line up these numbers? - 4 24
Slide 133 / 225 Subtracting Can you line up these numbers? - 6 58
Slide 134 / 225 Subtracting Can you line up these numbers? - 1 73
Slide 135 / 225 Subtracting Once the numbers are lined up, subtract the ones first and then the tens. Ones When there is no digit in the tens place, we know it is a 0. 0 2 7-4 It may help you to draw a line between the tens and ones. 2 3 It is important to line up the answer as well!!
Slide 136 / 225 Subtracting Remember to subtract the ones first and then the tens!!! When there is no digit in the tens place, we know it is a 0. 0 Ones 5 3-1 It may help you to draw a line between the tens and ones. It is important to line up the answer as well!!
Slide 137 / 225 Subtracting Remember to subtract the ones first and then the tens!!! Ones 79-8 It may help you to draw a line between the tens and ones. It is important to line up the answer as well!!
Slide 138 / 225 Subtracting Remember to subtract the ones first and then the tens!!! Ones 65-3 It may help you to draw a line between the tens and ones. It is important to line up the answer as well!!
Slide 139 / 225 Subtract Remember to subtract the ones first and then the tens!!! 9 6-5
Slide 140 / 225 Subtract Remember to subtract the ones first and then the tens!!! 3 5-3
Slide 141 / 225 Subtract Remember to subtract the ones first and then the tens!!! 2 6-2
Slide 142 / 225 Web Practice Click here for a game. Select level 4
Slide 143 / 225 41 3 9-7 A 32 B 31 C 36
Slide 144 / 225 42 1 4-3 A 17 B 7 C 11
43 7 7-5 Slide 145 / 225
44 8 4-3 Slide 146 / 225
45 2 7-2 Slide 147 / 225
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Slide 150 / 225 Two Digit Minus Two Digit Click to return to Table of Contents
Slide 151 / 225 Two Digit Subtraction What number is represented below?
Slide 152 / 225 Two Digit Subtraction 24 Now we want to take away 11 When we take away we always start with the bigger number.
Slide 153 / 225 First subtract the ones by crossing them out. tens ones - 2 4 1 1 How many are left?
Slide 154 / 225 Next cross out the tens tens ones - 2 4 1 1 3 How many are left?
Slide 155 / 225 Two Digit Subtraction tens ones - 2 4 1 1 1 3
Slide 156 / 225 Two Digit Subtraction What number is shown below?
Slide 157 / 225 Two Digit Subtraction 47 Now we want to take away 23 Remember we always start with the bigger number.
Slide 158 / 225 First cross out the ones tens ones - 4 7 2 3 How many are left?
Slide 159 / 225 Next cross out the tens tens ones - 4 7 2 3 4 How many are left?
Slide 160 / 225 Two Digit Subtraction tens ones 4 7-2 3 2 4
Slide 161 / 225 Subtract First cross out the ones. Next cross out the tens. What is the answer? tens ones - 3 4 3 1
Slide 162 / 225 Subtract First cross out the ones. Next cross out the tens. What is the answer? tens ones - 6 8 4 7
Slide 163 / 225 Subtract First cross out the ones. Next cross out the tens. What is the answer? tens ones - 5 2 3 2
Slide 164 / 225 Subtract First cross out the ones. Next cross out the tens. What is the answer? tens ones - 4 9 2 7
Slide 165 / 225 Roll the two set of dice. Place the larger number at the top of the problem. Place the second number under the first number. Subtract.
Slide 166 / 225 46 3 5-1 2 2 3 Yes No
Slide 167 / 225 47 6 9-5 6 3 3 Yes No
Slide 168 / 225 48 2 4-1 2 A 36 B 2 C 12
Slide 169 / 225 49 3 6-2 2 A 14 Draw base ten blocks to help you solve this problem. B 24 C 58
Slide 170 / 225 50 7 8-4 3 Draw base ten blocks to help you solve this problem.
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Slide 173 / 225 Two Digit Minus Two Digit Pt 2 Click to return to Table of Contents
Slide 174 / 225 Subtracting Two Digit Numbers When subtracting two digit numbers, it is important to still line up the numbers. 34-23 34-23
Slide 175 / 225 Subtracting Two Digit Numbers Once the numbers are lined up, draw a line between the tens and ones. First subtract the ones. Think of it as two smaller subtraction problems Tens Ones - 3 4 2 3
Slide 176 / 225 Subtracting Two Digit Numbers After you subtract the ones, subtract the tens! Tens Ones - 3 4 2 3 1 1 Don't forget to line up the answer too!
Slide 177 / 225 Let's try one! Tens Ones 7 6 4 5 -
Slide 178 / 225 Practice Tens Ones 3 6 5 2 -
Slide 179 / 225 Practice Tens Ones 6 4-1 4
Slide 180 / 225 Practice 5 7 Tens Ones - 2 1
Slide 181 / 225 Practice 6 5 Tens Ones - 3 3
Slide 182 / 225 Practice 7 2 Tens Ones - 2 0
Slide 183 / 225 Web Practice Click here for a game. Select level 6
Slide 184 / 225 51 6 8-3 6 A 94 B 32 C 31
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53 4 6-2 3 Slide 186 / 225
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Slide 188 / 225 Lab: Subtraction Spin Assemble spinners by cutting out the two circles and arrows. Attach the arrow to the center of the spinner with a brad. Have students work with a partner. Student 1 spins spinner A and write the number on the top line of the subtraction sentence. Repeat with spinner B and write the number under the first number. Student 1 solves the subtraction sentence on the paper while student 2 uses a calculator to check the answer. If student 1 is incorrect, have the students work together to find the mistake. Switch rolls and repeat. Click here for a more information Click to return to Table of Contents
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Slide 191 / 225 Word Problems Click to return to Table of Contents
Slide 192 / 225 There are 3 different types of subtraction problems 1. Take away 2. Comparison 3. Part/Part/Whole We solve all three by lining up the numbers on top of each other and subtracting.
Slide 193 / 225 Take Away Take away problems ask us to find how many are left. We start with a group of objects and take some away. There are 26 red birds on a fence and 14 fly away. How many are left? 26-14 =? xxxxxxxxxxxxxx
Slide 194 / 225 Part/Part/Whole In part/part/whole problems, we are looking for the missing part. Jim has 43 Skittles. 12 of them are red. How many are not red? 43-12 =? Whole 43 Part Part 12?
Slide 195 / 225 Comparison Comparison problems ask us to find the difference between two amounts. How many more? How many less? How much bigger? How much smaller? Jim has 45 pencils. Jess has 67 pencils. How many more pencils does Jess have? 67-45 =?
Slide 196 / 225 Word Problems Sometimes subtraction word problems require multiple steps. It is helpful to underline the 2 parts in different colors. Joe went to the store and bought 12 bananas and 21 apples. His sister ate 10 pieces of fruit. How many apples and bananas are left?
Slide 197 / 225 Word Problem Joe went to the store and bought 12 bananas and 21 apples. His sister ate 10 pieces of fruit. How many apples and bananas are left? In order to find how many are left, we need to first find out how many he started with. Step 1: How many pieces of fruit did Joe buy in all?? 12 + 21 =
Slide 198 / 225 Word Problem Joe went to the store and bought 12 bananas and 21 apples. His sister ate 10 pieces of fruit. How many apples and bananas are left? Step 2: How many pieces are left after his sister ate some?? 33-10 =
Slide 199 / 225 What type of problem is it? Bob went to the grocery store. He bought 18 hot dogs and 29 hamburgers for a party. How many more hamburgers did he buy than hot dogs?
Slide 200 / 225 What type of problem is it? Mom bought 36 items at the store. 23 of the items were frozen. How many items were not frozen?
Slide 201 / 225 What type of problem is it? Dad baked 24 cookies. Jim ate 13 of the cookies. His sister ate the rest. How many did his sister eat?
Slide 202 / 225 What type of problem is it? Billy had 16 puppies for sale. 14 of them were bought. How many are left?
Slide 203 / 225 What type of problem is it? There are 37 peanut butter cups in a bag. John ate 11 and Betty ate 14. How many are left?
Slide 204 / 225 What type of problem is it? Jess weighs 68 pounds. Her sister weighs 34 pounds. How much less does her sister weigh?
Slide 205 / 225 55 Which type of subtraction story is this? Jen had 27 nail polishes. 12 of them broke. How many are left? A Part/Part/Whole B Take Away C Comparison
Slide 206 / 225 56 Which two numbers would you add first? The pet store has 11 gray kittens and 26 white kittens. 14 kittens were bought. How many kittens are left? A 11 B 26 C 14
Slide 207 / 225 57 Ron has 67 dollars. He went to the store and spent 24 dollars. How much does he have left? A 91 B 34 C 43
Slide 208 / 225 58 The computer lab has 35 computers. A class comes and uses 22 computers. How many computers are not being used?
Slide 209 / 225 59 Bob has 57 flowers in his garden. Chris has 45 flowers in his garden. How many more flowers does Bob have? QUIZ
Directions: Slide 210 / 225 Lab: Subtraction Around the Room Print out one copy of the cards and laminate them. Cut out the cards and tape them around the room. Students move around the room looking for the subtraction problems. Students write and solve the subtraction sentence in the box numbered with the same number as the card. Click here for more information Click to return to Table of Contents
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Slide 213 / 225 Extra Word Problems Click to return to Table of Contents
Slide 214 / 225 Fruit Stand Prices 40 40 90 70 20 Use the above prices for each type of fruit to solve the following problems.
Slide 215 / 225 Fruit Stand Prices 40 40 90 70 20 You have 55 cents. You buy an apple. How many cents do you have left? 55-40
Slide 216 / 225 Fruit Stand Prices 40 40 90 70 20 You have 72 cents. You buy a pear. How many cents do you have left? 72-40
Slide 217 / 225 Fruit Stand Prices 40 40 90 70 20 You have 63 cents. You buy a strawberry. How many cents do you have left? 63-20
Slide 218 / 225 Fruit Stand Prices 40 40 90 70 20 You have 63 cents. You buy 2 strawberries. How many cents do you have left? - 63
Slide 219 / 225 Fruit Stand Prices 40 40 90 70 20 You have 90 cents. You buy a pineapple. How many cents do you have left?
Slide 220 / 225 60 You have 80 cents. You buy a tomato. How many cents do you have left? Farm Stand Prices 70 50 60 40 10
Slide 221 / 225 61 You have 70 cents. You buy a green pepper. How many cents do you have left? Farm Stand Prices 70 50 60 40 10
Slide 222 / 225 62 You have 70 cents. You buy a potato. How many cents do you have left? Farm Stand Prices 70 50 60 40 10
Slide 223 / 225 63 You have 90 cents. You buy an ear of corn. How many cents do you have left? Farm Stand Prices 70 50 60 40 10
Slide 224 / 225 64 You have 90 cents. You buy 4 carrots. How many cents do you have left? Farm Stand Prices 70 50 60 40 10
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