Counting by 10s, 20s, and 50s

Purpose

To build fluency at counting by 10s, 20s, and 50s.

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Materials

None

Overview

Ask children to count by 10s and count to 300. Next, count by 20s and 50s as a class.

Optional: Building a tower from the bottom up is a visual way to represent counting by numbers other than 1. You may choose to draw this as children are counting. For example, as you count by 20, add another brick of 20 to the tower. Children can see they need to add 20 to the running total (shown in green) to get to the new total. This visual model is useful in making a clear connection to the mental math.

About the sequence

Part 1, skip-counting by 10s, is likely familiar and just a warm-up. In Part 2, children use what they know to skip count by 20s. The extension—skip counting by 50s—builds a new skill.

Part 1

Let’s count by 10s, starting at 0. While we are skip-counting, we’ll we can do this for exactly thirty seconds, with one number each second and no faster.

0, 10, 20, 30, 40 … 270, 280, 290, 300.

If children need more practice or are enjoying their mastery, repeat. If children are ready to move on, move to Part 2.

Part 2

Count by 20s, starting at 0. While we are skip-counting, we’ll we can do this for exactly thirty seconds, with one number each second and no faster.

0, 20, 40, 60, 80,…540, 560, 580, 600.

If children need more practice, repeat. Or, when children seem excited for a new challenge, move to the extension.

Extension

Count by 50s, starting at 0. While we are skip counting, we’ll we can do this for exactly 30 seconds, with one number each second and no faster.

0, 50, 100, 150, 200…1,350, 1,400, 1,450, 1,500