## Explaining counting up and back - Section 2: Teaching the Lesson

*Explaining counting up and back*

# Math Treasure Hunt

Lesson 1 of 9

## Objective: SWBAT determine the operation needed to complete a math word problem and to solve it independently.

## Big Idea: Students have worked with models and strategies to solve a variety of math problems. Today they will need to use those strategies to complete the math tasks.

*65 minutes*

#### Warm Up

*15 min*

Today I begin by reviewing how addition is the opposite of subtraction. I put 4 subtraction number sentences on the board:

26 - 12=

19 - 11 =

22- 9 =

27 - 14=

I ask students to write in their math journals the addition sentences that go with the subtraction sentences and to solve both. I am asking them to make sense of the two problems and then to solve them (MP1). When students show with a thumbs up that they are mostly done, I say “Now that everyone has at least 2 of the problems done, lets share what we have done.” This validates that everyone has tried and done part of the task and it is alright not to be completely done. I ask for volunteers to come up and write the addition sentences they found. There will be 2 addition options so I allow for a second round of students to come up and tell what they have done. We talk about why both of these models work.

I remind students that they can use an addition number sentence to help them figure out a subtraction sentence or visa versa. Here I am introducing another way to make sense of math problems so students can solve them independently (MP1).

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#### Teaching the Lesson

*45 min*

Today I will have 3 homogeneous working groups. Students will spend about 15 minutes at each center. Today students will be working to solve math problems by modeling with mathematics (MP4), making sense of problems (MP1) and choosing the correct tools to measure (2MD.A.1)

- Learning to measure with a tape measure: In this group students will look at the tape measure and discuss how it is the same or different from a ruler and a yard stick. They will think of things that would be better measured with each of the tools. Students will move about the room and measure a variety of larger objects, such as a door, or the white board using the tape measure.
- Counting up or back for a subtraction problem using the number grid: In this group students will work with an adult to use a number grid for a subtraction problem. I ask them to think about whether they are counting up or back when they subtract (ie if the problem is 16 - 9, they could count on 10,11,12,13,14,15,16 to get 7, or they could count back 15,14,13,12,11,10,9 to also get 7. We talk about how both ways are good ways to solve subtraction problems and that sometimes one will be easier and sometimes the other will be easier.
- Treasure Hunt: The treasure hunt consists of addition, subtraction and comparison word problems written on small paper leaves and placed around the room. The students have an answer sheet to record their findings on. The answer sheet, when completed, gives a message. Students move independently from problem to problem, figuring out the answers and the message.

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#### Closing

*5 min*

I ask students to return to their seats. I ask for comments about the treasure hunt. How many students finished? Did they figure out the message? (If students are not done, I allow students to finish the next morning and ask others to keep the message a secret.)

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- UNIT 1: What and Where is Math?
- UNIT 2: Adding and Subtracting the Basics
- UNIT 3: Sensible Numbers
- UNIT 4: Sensible Numbers
- UNIT 5: Everything In Its Place
- UNIT 6: Everything in Its Place
- UNIT 7: Place Value
- UNIT 8: Numbers Have Patterns
- UNIT 9: Fractions
- UNIT 10: Money
- UNIT 11: The Numbers Are Getting Bigger
- UNIT 12: More Complex Numbers and Operations
- UNIT 13: Area, Perimeter and More Measurement
- UNIT 14: Length
- UNIT 15: Geometry
- UNIT 16: Getting Ready to Multiply
- UNIT 17: Getting Better at Addition and Subtraction
- UNIT 18: Strategies That Work

- LESSON 1: Math Treasure Hunt
- LESSON 2: Measurement and Symmetry
- LESSON 3: Adding and Subtracting with Lengths
- LESSON 4: Working with Larger Numbers
- LESSON 5: Larger Distances
- LESSON 6: How Big Is A Foot?
- LESSON 7: Bigger Than A Foot
- LESSON 8: Centimeters and Inches
- LESSON 9: Measuring in Centimeters