# Clip 3/13: Standard 5: Use Appropriate Tools Strategically Using Decimals Part A

## Overview

*Mathematically proficient students consider the available tools when solving a mathematical problem. These tools might include pencil and paper…[or] a calculator….*

Erika Isomura works with her 5th graders to develop their understanding of how decimals work. She begins her lesson having her students work in pairs to do a “calculate and check” mental math decimal task, using calculators to check, then evaluating their work with symbols and writing (e.g. “We disagree because,” “I have a question because”).

She reminds her students to do the mental math, then first discuss what they got “in their brains,” and then check with their calculators. As the pairs work, Erika circulates around the classroom and probes their thinking (e.g. “Did you agree? Did that make sense?”). This clip also relates to standard 3 (construct viable arguments & critique the reasoning of others).