# Clip 15/29: Day 2: Decimal Pre-Lesson Part D

## Overview

After finishing the “traditional” decimal lesson, Mia Buljan and Erika Isomura discuss a lesson focused on repeated divisions of 25,000 by 10, so that her students might notice the movement of the decimal point, a pattern that was “discovered” by one of Erika’s students the previous day.

Erika describes starting the discussion with that discovery to reinforce the validity of the student’s idea. At this point, most of the class was showing readiness for understanding the mathematical patterns of moving the decimal point.

Erika and Mia then discuss the plan for the second documented day of instruction, connecting the ideas from previous day to a card sort of quantities from smallest to largest.

Erika’s students grapple with how to prove that their answers are correct — for example, by rewriting decimals as fractions with common denominators to prove their answer.

Mia and Erika examine and discuss a prior card sort that prepared students for the day’s learning, looking at the work of several student pairs to diagnose the students’ understandings.

Finally, Erika and Mia look at two new tasks that challenge students to match representations of place value notation to the expressions from the number talks. Erika has included some blank cards so that students may write their own cards.