# Clip 27/29: Day 2: Decimal Post-Lesson Debrief Part E

## Overview

Erika Isomura and Mia Buljan examine a card sort from a particular pair of students, and describe the mathematical understandings represented by the work sample.

They debate whether the students are actually connecting the various representations, and they discuss the purpose of the card sort as a formative assessment — as well as the challenges inherent in creating one’s own formative assessments.

Mia asks Erika to describe the student misconceptions she was trying to highlight and uncover, and what strategies she saw students using that she wanted to “capture and move out to the whole class.”

Erika shares that she wanted to find out if her students understood quantity in decimal form — e.g., that .001 is smaller than .01 — and that her examples were designed to get at students’ understanding of magnitude.

Erika also connects the students’ understanding of money to their understanding of decimals, describing a few student pairs’ approaches and work in which their misconceptions became visible, and one instance in which a student used his own explanation to revise his own thinking.