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Rounding on the Number Line. Whole Numbers 1, 2, 3, 4 round down to the “ 0 ” number 5, 6, 7, 8, 9 round up to the “ 0 ” number.

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Presentation on theme: "Rounding on the Number Line. Whole Numbers 1, 2, 3, 4 round down to the “ 0 ” number 5, 6, 7, 8, 9 round up to the “ 0 ” number."— Presentation transcript:

1 Rounding on the Number Line

2 Whole Numbers 1, 2, 3, 4 round down to the “ 0 ” number 5, 6, 7, 8, 9 round up to the “ 0 ” number

3 Decimal Numbers 1.1, 1.2, 1.3, 1.4 round down to the “ 0 ” number 1.5, 1.6, 1.7, 1.8, 1.9 round up to the “ 0 ” number

4 Language of Rounding  “Rounding to the nearest ten” means the ten will stay the same or move up to the next ten. The other numbers to the right of the ten will become 0 s.  The ones numbers 1, 2, 3, or 4 will allow the ten to stay the same.  The ones numbers 5, 6, 7, 8, or 9 will make the ten move up to the next number.  The same procedure is followed regardless of which place value is being rounded.

5 Place Value Example of rounding in which the ten stays the same. This is often referred to as “rounding down.” Round 56,912 to the nearest ten. Ten Thousands ThousandsHundredsTensOnes

6 Place Value Example of rounding in which the ten moves up one. This is often referred to as “rounding up.” Round 56,917 to the nearest ten. Ten Thousands ThousandsHundredsTensOnes

7 Concept Definitions “Rounding to the nearest tenth” means the tenth will stay the same or move up to the next tenth. The other numbers to the right of the tenth will become 0 s.

8 Concept Definitions “Rounding to the nearest hundred” means the hundred will stay the same or move up to the next hundred. The other numbers to the right of the hundred will become 0 s.

9 Concept Definitions Decimal Numbers: zeros to the right of the last 1 – 9 digit may be dropped.

10 Relationships Why are there tens and tenths and not ones and oneths? TensOnestenths Ones multiplied by 10 Ones divided by 10

11 How do we know – round up? round down? The number to the right of the rounding place value tells the story. Always look to the right. That number dictates whether the rounding number will stay the same or move up one.

12 Rounding Examples, Steps, Questions Round 892 to the nearest hundred. 1. Underline the place value number that is to be rounded Look at the number on the right of the underlined number. That number is a 9. 9 is in the 5-9 group which makes the underlined number move up one. 3. All other digits change to

13 Rounding Examples, Steps, Questions Round to the nearest tenth. 1. Underline the place value number that is to be rounded Look at the number on the right of the underlined number. That number is 7. 7 is in the 5-9 group which makes the underlined number move up one. All other digits change to s on the far right of a decimal number may be dropped

14 Simplified Steps 1. Underline place value number to be rounded. 2. Look to the right. 3. Leave the underlined digit the same or increase it by 1 4. Replace the numbers to the right with zeros. 5. Explain the new rounded number.

15 Example Questions 1. What is the “round number” below and above 34? 2. Is 17 closer to 10 or 20 on the number line? 3. Is 1.4 closer to 1 or 2? 4. Is 256 closer to 200 or 300? 5. In rounding 245 to the nearest hundred, what numeral replaces the 4 and the 5? 6. What do you do with zeros on the right of a whole number? 7. What do you do with zeros on the right of a decimal number? 8. How do you know whether to round up or down? 9. What is the round number closest to 298? 10. Does 5 round up or down?

16 Rounding Rhyme Find your place Look next door Five or greater Add one more All digits to the front Stay the same All digits behind Zero is your name


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