Math Focus 4
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## CHAPTER 3: ADDITION AND SUBTRACTION

### Lesson 8: Regrouping before Subtraction

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

Solve subtraction problems by regrouping first.

Builds Upon

Student Book pages 88–91

Instructions for Use

Base Blocks Subtraction allows students to solve subtraction problems by regrouping using base blocks.

To use Base Blocks Subtraction, scroll down and click on its name. Then click on and read the “Instructions” at the upper right of the new screen, including “Cancelling blue and red blocks”, “Exchanging and grouping pieces”, and “Subtraction exercises”. The game is played similar to Base Blocks Addition, except that blocks are dragged to the right, and blue and red blocks are used cancel each other.

To use Learn Math Addition and Subtraction, click on the subtraction tab at top centre. Then move your mouse under the math problem in the centre of the screen. The pencil in the genie’s hand will move to that spot. Use the pencil to calculate and write the answer, regrouping as needed, then find and click on it in the 4 choices on the right. If your answer is right you will see “Yes” above the 4 choices and your answer in white. If not, you will see “No, Try Again” and your answer blacked out. Click on the correct answer and then on “New Problem” to play another round.

Number Monster for Subtraction lets students practice 2- and 3-digit subtraction involving regrouping.

To use Number Monster for Subtraction, scroll down and click on “Number Monster” on the bottom left. On the next screen that opens, click on “2 & 3 DIGITS” at top right. Read the instructions in the red area and then click on “A” to get a 2-digit number problem or “C” to get a 3-digit number problem. Mentally regroup as needed and subtract, or use pencil and paper. Type your answer in the empty answer box and click on “???”. If you are right, “Cool! You got it!” displays under the top face on the right. If not, Bummer!” and the answer displays under the bottom face on the right. Your score is shown below the answer box. To play another round, click on “A” or “C” again.

Subtracting Three Digit Numbers lets students practice subtracting 3-digit numbers.

To use Subtracting Three Digit Numbers, read the directions, scroll down to “Practice”, and click on “Start”. A pair of numbers will display at the left of the equals sign as a timer counts elapsed time in the “Report Totals” box below. Enter your answer in the box right of the equals sign and click on “check”. If correct, a new pair of numbers will be displayed. If not, an error box will display the correct answer. Click “OK” to resume play. You can vary the game by scrolling down to “Play” and clicking on one of the 3 yellow boxes on the left.

QUIA Math Journey lets students practice adding and subtracting 3- and 4-digit numbers.

To use QUIA Math Journey, read the directions, click “3-digit numbers” and “4-digit numbers” under
“Addition” or “Subtraction”, and click on “Begin the Game”. A problem will be displayed for you to solve. Your objective is to fly around the world, city by city, by solving problems like this. Although the problems must be answered exactly, estimate to check that each answer that you input into the empty answer box is reasonable before clicking on “Check Answer”. If an answer is right, you will score air distance travelled and receive a new problem. If it is wrong, you will miss your flight and be shown the correct answer. Click on “Continue” to get a new problem.  If you miss three flights, the game ends. To play a new game at any time, click on “Start over”.