Math Focus 3

# Surf for More Math

## CHAPTER 6: ADDITION AND SUBTRACTION

### Lesson 10: Adding and Subtracting to Solve Problems

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

Goal

Add and subtract 3-digit numbers to solve problems.

Builds Upon

Student Book pages 156–157

Instructions for Use

Enter any 3-digit number in the first white box at the right side of the screen, then press “Enter.” Enter another 3-digit number in the second white box, then press “Enter” to add the two numbers together. Look at the answer to the addition problem beneath the boxes. If any column has more than 9 in it, click “Regroup” to regroup the numbers. Keep clicking “Regroup” until there is no more than 9 in each column. Then click “Check” to check your answer. Click “New Problem” to enter a new set of numbers into the boxes.

Subtraction of 3-Digit Numbers asks students to enter 3-digit numbers, regroup them if needed, and subtract them.

Enter any 3-digit number in the first white box at the right side of the screen, then press “Enter.” Enter a smaller 3-digit number in the second white box, then press “Enter” again. Look at the columns to see if any regrouping is needed (if there is a smaller number in the top row). If so, click “Regroup” to regroup the blocks. Keep clicking “Regroup” until no more regrouping is needed. Then click “Subtract” to see the answer. Click “New Problem” to enter a new set of numbers into the boxes.

Base Blocks allows students to use base ten blocks to solve problems.

Use base ten blocks to build models of numbers to solve problems. Set the number of columns to 3 by clicking on the down arrow for columns at the bottom right. Click blocks at the top of the chart so that they appear in the columns below. The number currently represented in the chart will appear to the right of the chart. You may use 100s, 10s, or 1s. To delete one of the blocks, click and drag it into the garbage bin at the bottom right of the chart. To clear the chart, click “Clear.”