# Math in Focus

## Lesson Overview

Students have learned subtraction up to 100 in Grade 1, when they were taught the basic subtraction algorithm of subtracting from right to left. Students have also been taught to apply their knowledge of number bonds and place value to decompose and compose numbers in regrouping to find sums and differences.

## Lesson 1

Subtraction without regrouping

Students will be able to:

~ Use base-ten blocks to subtract numbers w/o regrouping.

~ Subtract from 3 digit numbers w/o regrouping.

~ Apply the inverse operations of addition and subtraction.

~ Solve real-world subtraction problems.

Students will apply relationships and properties of number. Use efficient, accurate, and generalizable methods to add and subtract multi-digit whole numbers.

## Lesson 2

Subtraction with regrouping in the Ones & Tens

Students will be able to:
~ Use base-ten blocks to subtract numbers with regrouping.
~ Subtract from 3 digit numbers with regrouping.

~ Apply the inverse operations of addition and subtraction.

~ Solve real-world subtraction problems.

Students will learn to add and subtract to solve a variety of problems. They will compose and decompose multi-digit numbers. They will also apply understanding of models of addition and subtraction.

## Chapter Background

In these lessons, students will learn two types of multi-digit subtraction: basic subtraction without regrouping and subtraction with regrouping. Students are taught subtraction with regrouping using base-ten blocks and place-value charts as concrete representations, aiding students in visualizing the regrouping of tens as ones, hundreds as tens and hundreds as tens and ones. The same strategy is applied in regrouping in the hundreds and tens places and regrouping in the hundreds, tens, and ones places. Students are also reminded that addition and subtraction are inverse operations so addition can be used to check subtraction.

Incorporating technology into this unit will include iPads and the SmartBoard during stations. Students will engage in both independent and teacher led stations that incorporate the use of technology to enhance understanding and mathematical development.