## CHAPTER 6: ADDITION AND SUBTRACTION

**Lesson 1: Estimating Sums**

**Goal**

Estimate sums of 2-digit numbers to solve problems.

**Instructions for Use**

Estimation Contraption asks you to estimate sums. Level 1 is most appropriate for you.

Click “Instructions” to read about estimating, then click “Play Game.” Before the time runs out, estimate the total. Type your estimate in the box, then click “OK.” When Level 1 is complete, click here to play again.

Estimating a Sum allows you to practise estimating sums of 2-digit numbers using tens.

Scroll down the page to the section marked “Practice,” then click “Start.” Read the numbers in the white boxes, and estimate their sum. Select the sum from the buttons. Beneath these buttons, a message will appear to tell you if you answered correctly or not. Then read the next problem in the white boxes beneath the “Start” button.