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Welcome to this IRSC Adult
Education Live Virtual Lesson
Diana Lenartiene, Ed. S.
moderator/instructor
Introducing… your virtual
classroom
6/10/2008; updated:
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What is rounding?
Rounding means changing a number to a given place
value so that all the digits to the right of that number
become zeros, that is why it is called rounding.
Example: Round 365 to the nearest ten.
Answer: 370
Notice that the 5 in 365 is now a zero, and the six has
moved up to a 7.
THE ROUNDING POEM
Find your number.
Look right next door.
4 or less just ignore.
5 or more, add 1 more.
Round this number to the nearest
ten thousand.
Find your number.
3 6 8,9 7 1
Circle the number in the ten
thousands place.
Round this number to the nearest
ten thousand.
Look right next door.
3 6 8,9 7 1
Draw an arrow to the right of the
number.
Round this number to the nearest
ten thousand.
4 or less, just ignore.
3 6 8,9 7 1
8 is larger than 4 so go to the next
line of the poem.
Round this number to the nearest
ten thousand.
5 or more, add 1 more.
+1
3 6 8,9 7 1
Add 1 to the 6.
Round this number to the nearest
ten thousand.
5 or more, add 1 more.
3 7 0,0 0 0
Add 1 to the 6 and all the numbers
to the right of the 7 become 0’s.
The Answer
368,971 rounded to the
nearest ten thousand is
3 7 0,0 0 0
Round this number to the nearest
thousand.
Find your number.
3 5, 3 2 7
Circle the number in the thousands
place.
Round this number to the nearest
thousand.
Look right next door.
3 5, 3 2 7
Draw an arrow to the right of the
number.
Round this number to the nearest
thousand.
4 or less, just ignore.
3 5, 3 2 7
Since 3 is less than 4 we do not change
the 5.
Round this number to the nearest
thousand.
4 or less, just ignore.
3 5, 0 0 0
Change the numbers to left of 5 to 0’s.
The Answer
35,327 rounded to the
nearest thousand is
3 5, 0 0 0
Round this number to the nearest
dollar.
Find your number.
$ 5. 8 7
Circle the number where the dollars
are.
Round this number to the nearest
dollar.
Look right next door.
$ 5. 8 7
Draw an arrow to the right of the
circled number.
Round this number to the nearest
dollar.
4 or less, just ignore.
$ 5. 8 7
8 is greater than 4 so go to the next
line of the poem.
Round this number to the nearest
dollar.
5 or more, add 1 more.
+1
$ 5. 8 7
Since 8 is greater than 5 add 1 to the
5.
Round this number to the nearest
dollar.
5 or more, add 1 more.
$ 6. 0 0
Change the 5 to a 6 and change all the
numbers to the right to 0’s.
The Answer
$5.87 rounded to the
nearest dollar is
$ 6. 0 0
ESTIMATION
Three Types of Estimation
1. Measurement Estimation
2. Quantity Estimation
3. Computational Estimation
1.
2.
If I can drive 326 miles on 15 gallons of
gasoline what is my approximate mpg?
Is 10 dollars enough to buy 5 drinks that
cost $2.19 each?
A Computational Estimate



Determine a number that is the approximation
of a computation.
Not a guess, involves some form of
reasoning.
Sometimes knowing if the result is more or
less than a number is sufficient.
Multi-Digit Numbers
1. Can be built upon or taken apart in a wide variety
of ways.
2. Use easier-to-handle parts of numbers to create
estimates.
3. Computation can then be done mentally.
Multi-Digit Numbers
1. Substitute “nice” numbers for hard ones
2. Computation can then be done mentally.
Computational Estimation
1. Use a variety of strategies developed over time
2. Find Real Examples of Estimation
3. Accept a Range of Estimates
4. Focus on Flexible Methods NOT Answers
Understanding
Computational Estimation
Use the Language of Estimation
“About” “Close”
“Just about”
“A little more than”
“A little less than”
“Between””
Understanding
Computational Estimation
Estimating Without Estimates
Over or Under?
37+75 Over or Under 100
712-458
Over or under 300
319/45 Over or under 6
1. If chicken is on sale for 1.04 per pound, how much would
you pay for a whole chicken that weighs 5.95 pounds?
2. How much rock can Bryce carry with his truck in eight
loads if his truck can carry 2 7\8 tons on each load?
1. $1.04 is close to one dollar, so we will round it to $1.00.
5.95 pounds is almost 6 pounds, so we will round it to 6.
Now we set up our estimated problem to get an estimated answer.
Our estimated answer is $6.00
2. There are 2 ways to do this one. A) Leave the 8 loads as 8, then
estimate the tons of rock to 3. B) Round the 8 loads to 10, then round
the tons of rock to 3.
Now, multiply your estimate. The answer is 24 tons for A or
30 tons for B. Why can these answers be different?
 We round numbers by finding the place value column we are
Asked to round to, then looking at the number at the right. If the
Number is 5 or more, raise the number by one and make all
numbers to the right zeros.
 We estimate by rounding all the numbers we have in aproblem
then solving the new rounded problem.
 An estimate is an approximate or close answer we use when we
Do not need the exact answer.
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Thank you for viewing this
presentation.
Diana Lenartiene, IRSC ABE
Instructor