# Chapter 4: CK-12 Algebra Explorations Concepts, Grade 2

**At Grade**Created by: CK-12

## Introduction

In these concepts, you will be introduced to seven key concepts of algebra and will practice your problem solving skills. There are seven concepts, and each one focuses on a key algebraic thinking strategy. You will focus on describing, identifying your job, planning, solving, and checking your thinking.

- 4.1.
## Which Boxes

- 4.2.
## What's the Weight

- 4.3.
## Circles and Arrows 2

- 4.4.
## Better Buy 2

- 4.5.
## Critter Trades

- 4.6.
## Function Machines 2

- 4.7.
## GEO Patterns

### Chapter Summary

## Summary

In these concepts we used proportional reasoning when we traded critters and when we computed the unit costs of items in order to determine the better buy. We thought about equality and inequality and wrote equations when we looked at pan balances and filled one side in order to maintain balance. We saw variables as unknowns when we replaced variables with values in order to determine the weight of various types of blocks on scales, and when we solved for unknowns in the circles and arrows diagrams. We also saw variables as varying quantities when we completed tables for functions. In all of the concepts, we practiced interpreting representations of mathematical relationships when we looked at pan balances, circle and arrow grid diagrams, tables of values, weight scales, and patterns of geometric shapes.