Lesson: Subtracting by Breaking Apart Ones Mathematics • 2nd Grade

In this lesson, we will learn how to subtract a 1-digit number from a 2-digit number by breaking apart ones and model this with equations.

Lesson Plan

Students will be able to

use part–whole models to help decompose numbers when subtracting a one-digit or two-digit number from a two-digit number with regrouping,
subtract a one-digit and two-digit number from a two-digit number using decomposition when there is regrouping,
count back to subtract a one-digit and two-digit number from a two-digit number when there is regrouping,
use decomposition and part–whole models to solve subtraction word problems.

Q1:

Help James take away 7 from 24 by breaking apart ones.

First, take away the 4 ones:

We need to take away 7, how many more should we take away?

Take away the remaining ones:

Q2:

If you know that , find .

Q3:

Use the given model to solve .