## CHAPTER 3: ADDITION AND SUBTRACTION

**Lesson 6: Estimating Differences **

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**

Use your own strategies to estimate differences.

**Builds Upon**

Student Book page 83

**Instructions for Use**

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

To use Home Run Derby Math, click on “Play Now” at upper left and then on “Addition” and/or “Subtraction” in the screen that opens. Read the instructions and then click on “Start”. Click on “Play” at the bottom right of the scoreboard that opens and look at the numbers displayed in the “1st” and “2nd” boxes above, and at the “+” or “−“ operation sign on the right. You have 15 seconds to estimate the sum or difference and then click on the “Your answer” box below and type it in. Afterwards, click on “DONE” at bottom right to see the solution. Next, click on “HIT” to see how far your ball went and how close your answer was to the solution. If your answer is not close enough or you fail to answer in time, your at bat will be recorded as a strike. Click on “NEXT AT BAT” at upper right to play another round. The game is over when either you successfully play all 9 innings or record 3 strikes against you. Begin a new game by clicking “Back” and then “Start”.

**Estimation Vally Golf** lets students practice estimating sums and differences.

To use Estimation Valley Golf, read the step-by-step directions in and below the drawing and then click on “Play Now!” at upper left. On the menu screen that opens click on either “Boy” or “Girl” on the upper left and then on “Putt” to begin play at the lowest level. A math problem appears next to the golf green. You have 10 seconds to estimate and enter the answer in the box provided and click on “Validate” or hit “Enter”. Your player will then strike the ball. When it stops a red message will tell you how close your answer is. Or, if you fail to answer in time, “That’s not a valid answer!!” will display. In both cases, click on “Next Stroke” to continue. If your answer is exactly right “Game Over” will display above your player’s head. Click on this button or “Menu” at lower left to start a new game. You can also click on “Junior” to raise the difficulty lever. Several holes are played at this level.

**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”.