# Rounding on the Number Line

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Rounding on the Number Line
Place Value

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

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

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 0s. 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.

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 Thousands Hundreds Tens Ones 5 6 9 1 2

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 Thousands Hundreds Tens Ones 5 6 9 1 7 2

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 0s.

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 0s.

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

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

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.

Rounding Examples, Steps, Questions
Round 892 to the nearest hundred. Underline the place value number that is to be rounded. 892 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 0. 900

Rounding Examples, Steps, Questions
Round to the nearest tenth. Underline the place value number that is to be rounded. 562.47 Look at the number on the right of the underlined number. That number is is in the 5-9 group which makes the underlined number move up one. All other digits change to 0. 562.50 0s on the far right of a decimal number may be dropped. 562.5

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

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

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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