## Reflection: Complex Tasks Comparing Temperatures A Math and Science Comparison Part II - Section 2: Teaching the Lesson

Comparison problems are much more difficult conceptually than are part-part-whole problems. Part of the reason for this is that it is possible to solve the problem with either addition or subtraction.

Common Core Standards expect students to persevere in solving problems (MP1). They also say that students should be able to solve problems within 100 that involve adding on or taking away. Comparison problems can use both of these processing, but grasping that you can add on or subtract from to find the difference or comparison is not always easy for students to understand. These are a form of change problems where we start with an amount (the larger or smaller number) we change something (getting to the other number by adding on or taking away) and we end with the other number (the second number we were given) so for example we start at 32 degrees, we count up on a number grid or number line counting each digit as we point to 33,34,35.. as we say 1,2,3,..  to get 28 and we arrive at the second temperature or 60 degrees.

I often use the visual of 2 towers. The first tower is one amount that I have. I put the second tower or amount next to it. I show how much taller one tower is than the other. I explain to students that we want to find out how much taller (or bigger, or hotter, etc.) one is than the other. The visual of the 2 towers next to each other helps students to conceptualize the idea of comparison and then they are comfortable counting up or down to find the difference.

The Idea of Comparisons
Complex Tasks: The Idea of Comparisons

# Comparing Temperatures A Math and Science Comparison Part II

Unit 17: Getting Better at Addition and Subtraction
Lesson 6 of 12

## Big Idea: Students need to see that math has interesting, practical applications. This lesson connects math and science in a way that encourages math reasoning (MP2) and modeling (MP4).

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Standards:
Subject(s):
Math, Number Sense and Operations, addition, subtraction, comparison, Operations
55 minutes

### Beth McKenna

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