Math Focus 4
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## CHAPTER 3: ADDITION AND SUBTRACTION

### Lesson 1: Solving Problems by Estimating

Use these interactive activities to encourage students to have fun on the Web while learning about addition and subtraction. Students can try these activities on their own or in pairs.

Goal

Estimate sums of 3-digit numbers to solve problems.

Builds Upon

Student Book pages 68–69

Instructions for Use

Base Blocks Addition allows students to solve addition problems by regrouping using base blocks.

To use Base Blocks Addition, scroll down and click on its name. Then click on “Instructions” at the upper right of the new screen and read “Addition exercises” and “Exchanging and grouping pieces”. Click on “Close” at the top when done and then on “Next Problem” at the bottom of the “Solve the problem” column on the right. A new problem will display in the column and also show as base blocks in the 4 place value columns to the left.  Add the ones columns by clicking and dragging a rectangle around 10 ones blocks to regroup them as a tens block. Then click and drag this tens block into the tens column. Now add the tens and hundreds columns in the same way as you follow each step in the “Solve the problem” column. You can then click on the up or down “Columns” arrows or on “Next problem” to begin another problem. You can also click on “Create Problem” at top right and then click on and drag blocks into position to make your own problem to solve. Avoid changing the “Dec. Places” and “Base” settings.

Home Run Derby Math lets students practice estimating sums and differences.