# Clip 2/29: Standard 1: Making Sense and Perseverance Using Measurement Part A2

## Overview

*Mathematically proficient students understand and use stated assumptions, definitions, and previously established results in constructing arguments. They make conjectures and build a logical progression of statements to explore the truth of their conjectures… They justify their conclusions, communicate them to others, and respond to the arguments of others.*

A group of 1st-grade students use their feet to count how many steps long four pieces of tape are. Tracy Sola asks the students why, if they are all measuring the same pieces of tape, did they end up with different numbers for the length. She then prompts students to have a discussion with their partner.

Students use their experiences measuring the tape and refer to the recorded numbers on anchor charts as they communicate with each other and make conjectures about why different students recorded different numbers.

Tracy further engages the students in Math Practice Standard 3 by asking them how they could use the recorded numbers to tell who in the class has big feet, medium feet, and small feet.

The students first take individual think time to formulate their thoughts, and then they communicate and justify their thinking with a partner.