 Math Focus 3  Student Centre • Surf for More Math • Try It Out • Web Quests  Teacher Centre  Parent Centre     ## CHAPTER 3: ADDITION AND SUBTRACTION STRATEGIES

### Lesson 8: Solving Problems by Acting Them Out

Goal

Solve addition and subtraction problems by acting them out.

Instructions for Use

Electronic Abacus provides an electronic abacus for you to act out any addition and subtraction problems.

Select “Entering Numbers,” then use the electronic abacus to add and subtract numbers from the total. The number being added or subtracted and the total will be shown in the grey box below. Note that you must move all of the counters on the first line before being able to move the counters on the second line, and so on.

Base Blocks Addition has you act out addition problems by moving and regrouping base blocks.

First, change the number of columns, at the bottom right, to 2 by clicking the down arrow twice. Read the addition problem on the right side of the screen, then regroup blocks or move them to solve the problem. Click on the screen to draw a box around 10 ones blocks to regroup them into 1 tens block. Then move the tens block into the appropriate column to show the answer below the addition problem. Click “Next Problem” to continue.

Base Blocks Subtraction has you act out subtraction problems by moving and regrouping base blocks.

First, change the number of columns, at the bottom right, to 2 by clicking the down arrow twice. Read the subtraction problem on the right side of the screen, then break apart blocks or move them to solve the problem. Move red blocks overtop of blue blocks to subtract (delete) the blocks. To break a tens block into 10 ones blocks, click and drag the block into the ones column. You may also regroup blocks by clicking on the screen to draw a box around ones blocks to group them into a tens block. After regrouping, move the block into the appropriate column and the correct answer will appear below the subtraction problem. Click “Next Problem” to continue.   