Estimating Sums

1
Estimating Sums
2
Our Standards
Maryland VSC Standard - 6.C.2.a Determine the
approximate sum of 2 numbers
Maryland Technology Literacy Student Standard
(MTLSS)
- 3.A.1.a Use technology tools, including
software and hardware, from a range of
teacher-selected options to learn new content or
reinforce skills.
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Why Round?

• When the question asks you
• to estimate.
• When the question asks
• about how many?

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Rounding Poem
Find your number. Look right next door. 4 or less
just ignore. 5 or more, add 1 more.
5
Round this number to the nearesttens place.
Find your number.
2 7 5
Circle the number in the tens place.
6
Round this number to the nearesttens place.
Look right next door.
2 7 5
Draw an arrow to the right of the number.
7
Round this number to the nearesttens place.
4 or less, just ignore.
2 7 5
5 is larger than 4 so go to the next line of the
poem.
8
Round this number to the nearesttens place.
5 or more, add 1 more.
1
2 7 5
Add 1 to the 7.
9
Round this number to the nearesttens place.
5 or more, add 1 more.
2 8 0
Add 1 to the 7 and all the numbers to the right
of the 8 become 0s.
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The Answer
2 7 5 rounded to the nearest ten is
2 8 0
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Round this number to the nearesthundreds place.
Find your number.
7 3 5
Circle the number in the hundreds place.
12
Round this number to the nearesthundreds place.
Look right next door.
7 3 5
Draw an arrow to the right of the number.
13
Round this number to the nearesttens place.
4 or less, just ignore.
7 3 5
3 is less than 4 so ignore the 7 and Dont
change it.
14
Round this number to the nearesttens place.
7 0 0
The 7 stays the same and all the numbers to the
right of the 7 become 0s.
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The Answer
7 3 5 rounded to the nearest hundreds is
7 0 0
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Estimation and Rounding
How can we use what we know about rounding to
estimate?
Estimating sums is best done by rounding the
addends, then adding?
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Estimation and Rounding
3,456
687
Step 1- Round the addends to the largest place
value both numbers have in common. What is the
largest place value in common?
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Estimation and Rounding
3,456
687
The hundreds place is the largest place value the
two addends share in common.
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Estimation and Rounding
3,456
687
Round both addends to the nearest hundred.
Use the poem to help.
Find your number.
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Estimation and Rounding
3,456
687
Look right next door.
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Estimation and Rounding
3,456
687
4 or less, just ignore.
Both the 5 and 8 are greater than 4, so move to
the next line of the poem.
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Estimation and Rounding
3,456
687
5 or more, add one more.
Both the 5 and 8 are 5 or greater, so add 1 to
the numbers in the hundreds place. (4 and 6)
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Estimation and Rounding
1
1
3,456
687
5 or more, add one more.
Both the 5 and 8 are 5 or greater, so add 1 to
the numbers in the hundreds place. (4 and 6)
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Estimation and Rounding
1
1
3,456
687
3,
Any number to the left remains unchanged. The 3
in 3,456 is unchanged.
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Estimation and Rounding
1
1
3,456
687
7
3,
5
Add the 1 to the place value you are rounding.
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Estimation and Rounding
1
1
3,456
687
3,
5
0
0
7
0
0
All of the remaining numbers to the right become
zeros.
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Estimation and Rounding
3,500
700
4,200
Finally, add the rounded numbers.
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Estimation and Rounding
3,456
687
4,200
The estimate is about 4,200.