MATHEMATICS 2 nd Grade Miss Seeger

Standard 1.1: Use the commutative and associative rules to simplify mental calculations and to check results. Standard 1.2: Relate problem situations to number sentences involving addition and subtraction. Standard 1.1: Use the commutative and associative rules to simplify mental calculations and to check results. Standard 1.2: Relate problem situations to number sentences involving addition and subtraction. OUR STANDARDS: OUR LEARNING OBJECTIVE: We will be able to change problem situations into number sentences and solve using addition and subtraction. We will be able to use the commutative and associative rules to check our answers. WHAT DOES THIS MEAN? We will…. Change problem situations (word problems) into number sentences Solve these problems using addition and subtraction Use commutative and associative rules to check answers We will…. Change problem situations (word problems) into number sentences Solve these problems using addition and subtraction Use commutative and associative rules to check answers

In a problem situation we need to look for important information. To help us, we are going to underline the important information. Linda went to the store and bought 6 apples. She already has 12 apples at home. How many apples does Linda have altogether? A problem situation is a word problem. Example: Linda went to the store and bought 6 apples. She already has 12 at home. How many apples does Linda have altogether?

A number sentence is a number plus (+) or minus (-) another number equals (=) a number. What does this look like?? = – 13 = 3 You read a number sentence just like you would a normal sentence. From left to right. As you read it, you read the numbers and symbols out loud, and it makes a complete sentence. Read the examples out loud with me. Seven plus three is ten. Sixteen minus thirteen is three.

This video will show you an example of how to create a number sentence with information given in a problem situation (word problem). Did you notice how they created a number sentence using the numbers in the word problem? This is what you will be doing on your own at the end of this lesson… so pay attention so you will be on target!

Juan went to the store and bought 6 apples. He already has 12 apples at home. How many apples does Juan have altogether? Are we going to add or subtract the apples?? Our example from earlier…

Juan went to the store and bought 6 apples. He already has 12 apples at home. How many apples does Juan have altogether? Why did we add the numbers? We added the numbers together because the “important information” in the problem situation told us to find “How many apples altogether?”

Watch this! This law means that the numbers can be moved around, and they will always equal the same number. Think of the word, “commute,” such as if your parents commute (drive) from your home to work. They will go back and forth, just like the numbers do. Do you think this law works for both addition and subtraction?

This law states that it doesn’t matter how you group the numbers when you add them together. They will always equal the same number. Think of the word “associate.” If you associate yourself with friends, you are grouped with each other. Do you think this law works for both addition and subtraction?

Commutative Law

REVIEW What is a problem situation? - A word problem What is a number sentence? - A number plus/minus another number(s) equals a number. Do you group the numbers together in the Associative Law or Commutative Law? - Associative Law When you change the order of the numbers, is it the Commutative Law or Associative Law? - Commutative Law

1.Underline the important information. 2.Create a number sentence. 3.Solve the number sentence. 4.Check your answer. ____ ____ = _____ Here are 24 cards. Are we going to add or subtract 9? Why? Juan collects baseball cards. He has 24 baseball cards, but gives 9 away to his friend. How many baseball cards does Juan have?

1.Underline the important information. 2.Create a number sentence. 3.Solve the number sentence. 4.Check your answer Here are 24 cards. Are we going to add or subtract 9? Why? Juan collects baseball cards. He has 24 baseball cards, but gives 9 away to his friend. How many baseball cards does Juan have?

Sarah and Luis are walking to school. Along the way, they find 16 rocks. Then, they find 7 more rocks. While at school, they find 6 more rocks! How many total rocks did they find? Are we going to add or subtract? Why? ___ ___ ___ = ____

Sarah and Luis are walking to school. Along the way, they find 16 rocks. Then, they find 7 more rocks. While at school, they find 6 more rocks! How many total rocks did they find? Are we going to add or subtract? Why? Associative Law: (16 + 7) + 6 = 16 + (7 + 6)

Daniela had 21 toy cars. She gave some away to her best friend, Gabby. Daniela now has 14 toy cars left. How many toy cars did Daniela give away? Think, Pair, Share Activity: Talk with your partner and say if we are going to add or subtract? What numbers do we add/subtract?

Daniela had 21 toy cars. She gave some away to her best friend, Gabby. Daniela now has 14 toy cars left. How many toy cars did Daniela give away? Think, Pair, Share Activity: Talk with your partner and say if we are going to add or subtract? What numbers do we add/subtract? These are the 14 cars she has left So how many cars were given away? 21 - ? = = 14 Daniela gave 7 toy cars away.

I went to the store and bought 4 chocolate bars. Then, I went to another store and bought 15 more. When I got home I realized I already had 10 chocolate bars! How many chocolate bars do I have in total now? Jack swims 5 laps in a swimming pool. His sister swims 5 more laps than him. How many laps did his sister swim? Maria made 29 tacos. She gave 12 away. How many tacos does Maria have left? In our class, 12 students like pizza and 22 students like spaghetti. How many more students like spaghetti than pizza?

I went to the store and bought 4 chocolate bars. Then, I went to another store and bought 15 more. When I got home I realized I already had 10 chocolate bars! How many chocolate bars do I have in total now? Jack swims 5 laps in a swimming pool. His sister swims 5 more laps than him. How many laps did his sister swim? Maria made 29 tacos. She gave 12 away. How many tacos does Maria have left? In our class, 12 students like pizza and 22 students like spaghetti. How many more students like spaghetti than pizza? = = = = 10