Slide 1 / 225 Slide 2 / 225 1st Grade Two Digit Subtraction 2015-11-30 www.njctl.org Slide 3 / 225 Table of Contents click on the topic to go to that section - Subtracting Ten on a Number Grid - Subtracting Ten Patterns - Patterns When Subtracting Multiples of Ten - Two Digit Minus One Digit - Subtracting Ten from Multiples of Ten in Our Head - Two Digit Minus Two Digit - Two Digit Minus Two Digit Pt. 2 - Word Problems - Subtracting Ten from Multiples of Ten with Blocks - Subtracting Multiples of Ten with Blocks - Subtracting Ten with Blocks - Subtracting Multiples of Ten on a Number Grid - Extra Word Problems (If needed) - Lab: Subtraction Dice Roll - Lab: Subtraction Spin - Lab: Subtraction Around the Room Slide 4 / 225 Standards for Mathematical Practices MP 8 Look for and express regularity in repeated reasoning. 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. 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 Slide 5 (Answer) / 225 Subtracting 10 from Multiples of 10 with Blocks Click to return to Table of Contents Teacher Notes [This object is a teacher notes pull tab] Students will need base ten blocks and place value charts for this lesson.
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Slide 1 / 225 Slide 2 / 225
1st Grade
Two Digit Subtraction
2015-11-30
www.njctl.org
Slide 3 / 225
Table of Contents click on the topic to go to that section
- Subtracting Ten on a Number Grid- Subtracting Ten Patterns
- Patterns When Subtracting Multiples of Ten
- Two Digit Minus One Digit
- Subtracting Ten from Multiples of Ten in Our Head
- Two Digit Minus Two Digit- Two Digit Minus Two Digit Pt. 2
- Word Problems
- Subtracting Ten from Multiples of Ten with Blocks
- Subtracting Multiples of Ten with Blocks
- Subtracting Ten with Blocks
- Subtracting Multiples of Ten on a Number Grid
- Extra Word Problems (If needed)
- Lab: Subtraction Dice Roll
- Lab: Subtraction Spin
- Lab: Subtraction Around the Room
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Standards for Mathematical Practices
MP 8 Look for and express regularity in repeated reasoning.
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.
Click on each standard to bring you to an example of how to meet
this standard within the unit.
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Subtracting 10 from Multiples of 10 with Blocks
Click to return to Table of Contents
Slide 5 (Answer) / 225
Subtracting 10 from Multiples of 10 with Blocks
Click to return to Table of Contents
Teac
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[This object is a teacher notes pull tab]
Students will need base ten blocks and place value charts for this lesson.
Discuss how the tens place changed but not the ones since we subtracted 10s.
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30 - 20 = 10
Slide 117 (Answer) / 225
30 - 20 = 10
Teac
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[This object is a teacher notes pull tab]
Review how the tens place changed when we subtracted
10.
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What number is this?
What digit changed?
Take 40 away and what number does it become?
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What number is this?
What digit changed?
Take ten away and what number does it become?
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Count back by 10s
60, 50, ___, ___, ___, ___
70, 60, ___, ___, ___, ___
40, 30, ___, ___, ___, ___
60, 50, ___, ___, ___, ___
Slide 120 (Answer) / 225
Count back by 10s
60, 50, ___, ___, ___, ___
70, 60, ___, ___, ___, ___
40, 30, ___, ___, ___, ___
60, 50, ___, ___, ___, ___
Teac
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[This object is a teacher notes pull tab]
Review that when counting by 10s, the tens place goes down 1 and the ones place
stays the same.
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40
206030
8070
What number is 20 less?
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36 10 less than 50 is 5?
True
False
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36 10 less than 50 is 5?
True
False
[This object is a pull tab]
Ans
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False
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37 20 less than 90 is 80?
Yes
No
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37 20 less than 90 is 80?
Yes
No
[This object is a pull tab]
Ans
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No
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38 What is 30 less than 40?
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38 What is 30 less than 40?
[This object is a pull tab]
Ans
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10
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39 What is 40 less than 50?
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39 What is 40 less than 50?
[This object is a pull tab]
Ans
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10
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40 70 - 40 = ?
QUIZ
Slide 126 (Answer) / 225
40 70 - 40 = ?
QUIZ
[This object is a pull tab]
Ans
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30
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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 to return to Table of Contents
Click here for more information.
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Two Digit Minus One Digit
Click to return to Table of Contents
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When subtracting a 1 digit number from a 2 digit number, it is very important to line them up on top of
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.
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?
Word Problems
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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 1: How many pieces of fruit did Joe buy in all?
12 + 21 = ______?
In order to find how many are left, we need to first find out how many he started with.
Word Problem
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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 1: How many pieces of fruit did Joe buy in all?
12 + 21 = ______?
In order to find how many are left, we need to first find out how many he started with.
Word Problem
Teac
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[This object is a teacher notes pull tab]
Click on the ? to show the addition problem.
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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 = ______?
Word Problem
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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?
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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?
Teac
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[This object is a teacher notes pull tab]
Work through the problems with the students. Take time
to discuss what type of problem it is. Have students
work on the problems at their desks while another
student completes it on the board.
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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?
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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?
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What type of problem is it?
Billy had 16 puppies for sale. 14 of them were bought. How many are left?
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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?
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What type of problem is it?
Jess weighs 68 pounds. Her sister weighs 34 pounds. How much less
does her sister weigh?
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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
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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[This object is a pull tab]
Ans
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B
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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
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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
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Ans
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A and B
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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
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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[This object is a pull tab]
Ans
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C
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58 The computer lab has 35 computers. A class comes and uses 22 computers. How many computers are not being used?
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58 The computer lab has 35 computers. A class comes and uses 22 computers. How many computers are not being used?
[This object is a pull tab]
Ans
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13
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59 Bob has 57 flowers in his garden. Chris has 45 flowers in his garden. How many more flowers does Bob have?
QUIZ
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59 Bob has 57 flowers in his garden. Chris has 45 flowers in his garden. How many more flowers does Bob have?
QUIZ
[This object is a pull tab]
Ans
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12
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Lab: Subtraction Around the RoomDirections:
· 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.