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Number Sense and NumerationPowerPoint Presentation

Number Sense and Numeration

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### Number Sense and Numeration

Quiz #1 recap

Rounding Numbers

Now that we understand that parts of numbers have different place values, we can use that information to help us round numbers either up or down

We can round numbers to the nearest ten, hundred, thousand, or ten thousand

Remember, we look at the number to the right of the number we are rounding to decide what to do with it

Rounding Numbers (continued)

If the number to the right of the number we are rounding (no matter what place value it is) is 5 or higher, we round up (the number increases by 1) and if it is 4 or lower, we round down (the number stays the same)

For example, if you are asked to round to the nearest hundred, you will look at the number in the tens column to figure out what to do with the hundreds number

Once you have figured out whether to round the number up or down, do that, but also remember to make all the numbers to the right of the rounded number into zeros

Practice with Rounding to Different Place Values

Round this number to the nearest ten thousand:38 495

40 000

Now round it to the nearest thousand

38 000

Now round it to the nearest hundred

38 500

And lastly, round it to the nearest ten

38 500 ***notice that because the number in the tens column is a 9 and the number to the right of the 9 is a 5, we would round up, however, a 9 can only go up to a ten so we have to carry it over to the hundreds column, just like when we add***

More Practice with Rounding

Round this number to the nearest ten thousand:164 934

160 000

Now round it to the nearest thousand

165 000

Now round it to the nearest hundred

164 900

And lastly, round it to the nearest ten

164 930

Important Terms

STANDARD FORM – The way we usually write numbers (using numbers). When numbers greater than 9999 are written in standard form, the thousands part is separated from the rest of the number with a space to make it easier to read (e.g. 10 000) SPACE

EXPANDED FORM – A way to write a number that shows the value of each digit (e.g. In expanded form, 2365 is 2000+300+60+5 or 2 thousands 3 hundreds 6 tens 5 ones.)

More Practice with Expanded Form

Write the number 21 341 in expanded form

20 000 + 1 000 + 300 + 40 + 1

Write the number 50 120 in expanded form

50 000 + 100 + 20

Write the number 52 003 in expanded form

50 000 + 2 000 + 3

Write the number 19 456 in expanded form

10 000 + 9 000 + 400 + 50 + 6

Write the number 564 882 in expanded form

500 000 + 60 000 + 4 000 + 800 + 80 + 2

One More Important Term

WRITTEN FORM – When you are asked to write a number “in words”, you have to write it out using words (e.g. 27 894 would be written in words as “twenty-seven thousand eight hundred ninety-four”

Use hyphens (this symbol –) when you are writing a number that would normally be 2 numbers read together, like twenty-seven (27) or sixty-eight (68), we call these compound numbers

Writing Numbers in Words and Using the Word “and”

The word “and” is only used when writing numbers with decimal points

This is important because the “and” is actually used to tell us there is a decimal point in a number

You should NOT use the word and when writing out whole numbers in words

For example, the number 475 is written as:four hundred seventy-five ***don’t forget the hyphen for compound numbers!!***

475 would NOT be written as:four hundred and seventy-five

Practice Writing Numbers in Words

Write the number 8935 in words

eight thousand nine hundred thirty-five

Write the number 649 092 in words

six hundred forty-nine thousand ninety-two

Write the number 158 in words

one hundred fifty-eight

Write the number 7463 in words

seven thousand four hundred sixty-three

Write the number 16 961 in words

sixteen thousand nine hundred sixty-one

Practice Writing Numbers in Words using Decimal Numbers

Write the number 8935.67 in words

eight thousand nine hundred thirty-five andsixty-seven hundredths

Write the number 649 092.9 in words

six hundred forty-nine thousand ninety-two andnine tenths

Write the number 158.95 in words

one hundred fifty-eight andninety-five hundredths

Write the number 7463.15 in words

seven thousand four hundred sixty-three and fifteen hundredths

Write the number 16 961.346 in words

sixteen thousand nine hundred sixty-one and three hundred forty-six thousandths

Writing Numbers vs. Saying Numbers

Please remember that writing numbers follows a different formula than saying them, especially when those numbers use decimals

We would not read the number 16 961.346 as “sixteen thousand nine hundred sixty-one and three hundred forty-six”, we would read it as “sixteen thousand nine hundred sixty-one decimal three four six”

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