Adding_and_Subtracting_Decimal_numbers_1.ppt
- 1. Largest Number • Using the following numbers: 5,3,7,4,2,1 create the largest sum possible. Each number has one decimal in it. • Example: 12.3 + 98.4 = 110.7 Decimals:
- 2. Place Value • The decimal divides the whole numbers from the parts. Think money. The decimal divides the dollars from the cents.
- 3. Rounding • To round any number, you use the place value to the right to determine if the number will increase or stay the same. • Example: • 1458.023508 • I want to round the thousandths place. I need to look to the place to the right of the thousandths place to determine what happens to the number in the thousandths place.
- 4. Guided Practice • Round to the tenths place: 245.2653 • Round to the hundreds place: 12356.369 • Assessment Prompt: What two things do we need to know to be able to round a number?
- 5. Computing with Decimals Adding and Subtracting Decimals Multiplying Decimals Dividing Decimals
- 6. Adding and Subtracting Decimals Step 1: Line up the decimals in the addends 9.8 + 2.12 Step 2: add or subtract as normal. 9.80 + 2.12 11.92 Before or after you add or subtract you need to bring the decimal straight down. You may add a 0 to hold the place value.
- 7. Adding and Subtracting Decimals Step 3: If there are no decimals, then you are either adding or subtracting a whole number. Remember the decimal is behind the whole number. 6.93 + 3 = Step 4: When subtracting, you may need to add zero place holders to help you borrow. 3 - .123
- 8. Adding and Subtracting Decimals Helpful Hints: Think of decimal numbers as dollar amounts. This may help you remember where to line up the decimals. Rules for adding and subtracting are the same for decimals as for whole numbers. Whole numbers have decimals behind them. We normally do not write them. Ex: 12 = 12.0 Don’t forget to put a decimal in your answer.
- 9. Adding and Subtracting Decimals Your Turn: 2.3 12.06 + 1.03 - 11.1 3.236 1.3 + 1 - .265 7.5 + 6 = 4 - .67 =
- 10. Error Analysis 1 3 . 2 1 5 - 6 .2 1 3 . 1 5 3 11 1
- 11. Domino Addition • Each student will have one domino. You will match with another student to create and solve a decimal addition problem. You will do this 3 times. • Put the partners’ names beside each problem.
- 12. Summarizer • What is the procedures for adding and subtracting decimals?