---
title: "Choosing a tool or representation"
description: "Select and use appropriate tools and representations (number lines, hundred squares, rulers, part-whole models) to support problem-solving"
canonical: https://lightmysky.com/learn/mathematics/choosing-a-tool-or-representation-mt_zMEvtigoM3
source: https://lightmysky.com/learn/mathematics/choosing-a-tool-or-representation-mt_zMEvtigoM3.md
retrieved: 2026-09-02
---

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# Choosing a tool or representation

Select and use appropriate tools and representations (number lines, hundred squares, rulers, part-whole models) to support problem-solving

Subject: Mathematics · Area: Mathematical Thinking · Ages 6 to 7
Page: https://lightmysky.com/learn/mathematics/choosing-a-tool-or-representation-mt_zMEvtigoM3

## Ready when they can

- Choose a number line or hundred square to support adding or subtracting two-digit numbers
- Select a ruler when a problem requires measuring length
- Explain why one representation (e.g. a number line vs cubes) is more helpful for a particular problem

## Lesson: Picking the right tool

Not every problem is best solved in your head. A number line, a hundred square, or a ruler can help you see the answer instead of guessing.

*(drawing: A number line helps you hop from one number to another, like hopping from 24 to 34 by adding 10.)*

A number line lets you hop from one number to another, so it fits adding and subtracting. A hundred square lays every number out in rows of ten, so adding ten means dropping one row straight down. Both tools show each step, so you do not lose track while you count.

**Example.** Mia needs to measure her book, so she picks up a ruler, not a number line, because a ruler is made for measuring length. Then Mia needs to add 36 and 20, so she picks a hundred square and counts on two rows. She chose a different tool for each job.

**Tip.** Ask yourself: am I measuring something, or am I adding and subtracting numbers? That tells you which tool to reach for.

**Recap.** Pick the tool that matches the problem: a ruler for length, a number line or hundred square for adding and subtracting.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Hands-On Problem Solving](https://lightmysky.com/learn/mathematics/hands-on-problem-solving-mt_20WfHhnL39)
- [Measuring length (age 6+)](https://lightmysky.com/learn/mathematics/measuring-length-age-6-mt_cqSf213hSa)
- [Adding within 100](https://lightmysky.com/learn/mathematics/adding-within-100-mt_glPPG-kTQY)

## Opens up

- [Choosing the right strategy](https://lightmysky.com/learn/mathematics/choosing-the-right-strategy-mt_mQcWGh02no)