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Adding and Subtracting Whole Numbers and Decimals
Topic 2
EnVision Math
Rounding Numbers
The rounding poem
Find your number
Look right next door
4 or less, just ignore
5 or more add one more!
Write this poem
down in your notes!
Rounding Whole Numbers
Round 474 to the closest hundred.
474 Find your number
Look right next door
Four or less, just ignore
Five or more, add one more
474 Rounded to the hundreds becomes 500
Round 474 to the closest 10’s
474
Just ignore = 470
What about decimal numbers
The same rules (and poem) apply!
Round 4.167 to the closest hundredths
4.167 Find your number
Look right next door
4.17 or 4.170 Four or less, just ignoreFive or more, add one more
Remember
If you are asked to round to the nearest tenth…….your answer
stops in the tenths place!
Example: Round 42.73 to the closest tenth would be 42.7
Special Case!Rounding a 9
Round 2.197 to the hundredths place
Since there is a “9” in the hundredths place consider the tenth and hundredths together – 19 – do you leave it at 19 or move it to 20?
Round 4.95 to the closest tenth
Since there is a “9” in the tenth spot consider the ones and tenths together…… should you leave it at 49 or move it to 50?
4.95 rounded to the nearest tenth is 5.0
Try these
Round to tenthstenths:
4.56 4.6
5.32 5.3
0.98 1.0
Round to hundredthshundredths
18.784 18.78
9.456 9.46
9.997 10.00
Mountain Mathpractice….
This is called the “Brown Board”because it has brown paper as thebackground….
Brown Board Questions~~1a. Write the number1b . Is this number even or odd?1c. Round this # to the nearest ten1d. Round this # to the nearest hundred1e. Round this # to the nearest thousand1f. Round this # to the nearest ten thousand1g. What number is 100 less than this #1h. What number is 100 more than this #1i . What number is 1000 less than this number1j. What number is 1000 more than this number1k. Write this number in expanded form2. Write this number
Answer these questions together—whole group
1a 27,9591b odd1c 27,9601d 28,0001e 28,0001f 30,0001g 27,8591h 28,0591i 26,9591j 28,9591k 20,000 + 7,000 + 900 + 50 + 92 809.004
~Answers~
** All of the questions 1b-1krefer to the originalnumber on 1a
And….this is called the “White Board” because….You guessed it…it has a white background.
Mountain Math Questions ~~ White Board ~~
1a) Write this number.1b) Round to the nearest whole number.1c) Round to the nearest tenth.1d) Round to the nearest hundredth.1e) Round to the nearest thousandth.1f) Round to the nearest ten thousandth.1g) Name the place of the last digit.1h) Write this number in word form.
Answer these questions together—whole group
1a) 4.493711b) 4.01c) 4.51d) 4.491e) 4.4941f) 4.49371g) hundred thousandths1h) four and forty-nine thousand three hundred seventy-one hundred thousandths
Again, all of theseanswers refer to the number on 1a
Answer these Questions –for a grade
Brown Board White Board
Answers to Mtn. Math questions
1a) 203,1231b) odd1c) 203,1201d) 203,1001e) 203,0001f) 200,0001g) 203,0231h) 203,2231i) 202,1231j) 204,1231k) 200,000 + 3,000 + 100 +
20 + 32) 2.90
1a) 18.7329641b) 19.01c) 18.71d) 18.731e) 18.7331f) 18.73301g) millionths1h) eighteen and seven hundred
thirty-two thousand nine hundred sixty-four millionths
Brown BoardWhite Board
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