## Lesson: Adding and Subtracting Decimals

Developing the Concept

As long as students remember to align the numbers at the decimal point (or the ones place) in addition and subtraction problems, they should do as well with decimal computation as they do with whole-number computation. This game gives students a chance to generate decimal numbers, write and solve problems, and check decimal addition and subtraction.

**Wrap-Up and Assessment Hints**

Present an exercise involving different numbers of decimal places either orally or in equation form. Ask students to do the following.

- Write the exercise in preparation for computing.
- Explain how they lined up the digits.
- Compute and explain each step of the computation.
- Write a paragraph explaining how this computation is similar to computing with whole numbers.

If students have trouble writing mathematics, you could get them started by asking them to show the work to you and tell you what they're doing. You might even want to let them make a video in which they narrate their progress through the computation. (The camera will have to aim over the student's shoulder so you can see that the explanation is clearly related to the work.)