Unit 2, Lesson 1

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Unit 2, Lesson 1

• Addition Facts Strategies

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Goals

• Commutative and associative properties of
  addition
• Practice addition facts strategies

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What We Will Learn Today

• We are going to learn that we can add numbers in
  any order and still get the same answer.
• That can group numbers together any way we want
  when we add.
• It is easier to add numbers when you make groups
  of ten.

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Using a Ten

• You will work in pairs.
• Each pair will have 40 connecting cubes.
• Materials getters, please get a bag of cubes and
  give 4 trains of 10 to each pair in your group.
  Please make sure that they have four different
  colors.

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Using a Ten

• You have enough cubes for you to do some of these
  activities on your own.
• Some of the activities will require that you work
  together with your cubes.

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Using a Ten

• I want each student to take two different colors
  of connecting cubes.
• Build one train with 7 cubes of one color.
• Building another train with 8 cubes of another
  color.

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Using a Ten

• What can you do with your cubes to make a train
  of ten?
• Yes, move two cubes from the train of seven cubes
  to the train of eight cubes.
• Or, move three cubes from the train of eight
  cubes to the train of seven cubes.

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Using a Ten

• You now have a train of 10 cubes and a train of 5
  cubes. What is the sum?
• 15
• Why is this problem (10 5) easier to solve than
  the first one (7 8)?

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Vocabulary

• Addend a number that is added to another
• Sum the answer to an addition sentence

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Teaching the Activity

• Do the following problems by making a train of
  one color for the first addend and a train of
  another color for the second addend.
• 6 7
• Why is 10 3 easier to solve than
• 6 7?

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Teaching the Activity

• 8 8
• Why is 10 6 easier to solve than 8 8?

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Teaching the Activity

• 8 9
• Why is 10 7 easier to add than 8 9?
  

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Switch It!

• These next problems you will have to do in pairs.
• Solve 14 7 6 with connecting cubes. Use a
  different color for each addend.
• Group the cubes in as many tens as possible.

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Switch It!

• What can you do with the train of 14?
• What can you group together to make a ten?
• What is your answer?

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Switch It!

• Lets share your solutions.

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Challenge

• Try to add 14 7 6 using mental arithmetic.
• See if you can rearrange any of the numbers to
  make groups of ten.
• How did you solve this without paper, pencil or
  cubes?

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More Problems

• Do these problems first with mental addition.
  Try to find groups of 10. You may also use
  doubles.
• Then use your cubes.
• 8 7 12
• 6 8 14
• 11 3 9

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Vocabulary

• Partition To divide into parts.
• Ex 7 can be divided into 5 and 2

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Breaking Addends into Parts

• Sometimes addends can be easily grouped into
  tens.
• Sometimes this isnt easy to see.
• Try partitioning addends before finding groups of
  ten.

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Breaking Addends into Parts

• Example 7 5 2
• The second addend, 5, can be rewritten as 3 2.
• 7 3 2 2
• What two numbers can you group together to make
  10?
• What is the sum?

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Breaking Addends into Parts

• Work with your partners to solve the following
  problems.
• Use your math notebook to write the number
  sentence and then show how you partitioned the
  number.

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Breaking Addends into Part

• 6 8 3
• 9 7 2
• 4 9 3
• Lets compare your solutions.

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My Calculator is Broken

• We are going to imagine that some of the keys on
  the calculator are broken.
• That means that you cannot use those keys.
• .

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My Calculator is Broken

• First, lets imagine the five is broken.
• What keys would you press to do the problem 9 5
  2?
• Share your solutions.

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My Calculator is Broken

• Do these additional problems without using the 5
  key.
• 8 5
• Share your solutions
• 5 7 6
• Share your solutions

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My Calculator is Broken

• 15 6 3
• Share your solutions
• 9 25
• Share your solutions

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What We have Learned

• We learned that we can add numbers in any order
  and still get the same answer.
• We can group numbers together any way we want
  when we add.
• It is easier to add numbers when you make groups
  of ten.