# Lesson 18 1 More or 1 Less with Towers and Numbers

Let’s find 1 more or 1 less than a number.

## Warm-up Act It Out: Forks for Dinner

Mai is helping hand out the forks for dinner.

There are 9 people sitting at the table.

Mai has 7 forks.

Are there enough forks for each person to get one?

## Activity 1 What’s Missing?

Put your towers and numbers in order from 1–10. Put the number under each tower.

Now one person will close their eyes and their partner will remove one tower and the number that matches and hide them behind their back.

Open your eyes. Which number and tower are missing? How do you know?

## Activity 2 One Less, One More

my tower

my partner’s tower

my tower

my partner’s tower

my tower

my partner’s tower

my tower

my partner’s tower

## Activity 3 Centers: Choice Time

Choose a center.

Math Stories

Math Libs

Number Race

## Practice Problem

## Problem 1

Here is a connecting cube tower that Mai made.

Write a number to show how many cubes are in Mai’s tower.

Build a tower that shows 1 more cube than Mai’s tower.

Write a number to show how many cubes are in the new tower.Build a tower that shows 1 less cube than Mai’s tower.

Write a number to show how many cubes are in the new tower.