Download Estimate Differences

© 2007 M. Tallman
Step 1:
Circle the digit in
the place that you
must round to.
Step 2:
Draw an arrow to
the place on the
right.
Round to the nearest thousands place.
7,286
Findright
yournext
number.
Look
door.
© 2007 M. Tallman
Step 1:
Circle the digit in
the place that you
must round to.
Step 2:
Draw an arrow to
the place on the
right.
Step 3:
If the number is
four or less, then
the circled number
stays the same.
Step 4:
All numbers to the
right of the circled
number become
zeros.
Round to the nearest thousands place.
000
7,286
Just
Ignore!
2 is less
than 4
4 or less, just ignore.
© 2007 M. Tallman
Step 1:
Circle the digit in the
place that you must
round to.
Step 2:
Draw an arrow to the
place on the right.
Round to the nearest hundreds place.
1 ,792
Findright
yournext
number.
Look
door.
© 2007 M. Tallman
Step 1:
Circle the digit in the
place that you must
round to.
Step 2:
Draw an arrow to the
place on the right.
Step 3:
If the number is four
or less, then the
circled number stays
the same.
Step 4:
If the number is 5 or
greater, then add 1 to
the circled number.
Step 5: All numbers
to the right of the
circled number
become zeros.
Round to the nearest hundreds place.
1 ,7
892
00
7+1=8
9 is not
less than 4
ormore,
less, just
ignore.
54or
add 1
more.
© 2007 M. Tallman
When to use estimation…
When an exact answer is not needed.
When you need to compute a problem
quickly.
To check your work.
© 2007 M. Tallman
496 - 112
The actual
answer is 384,
so our
estimation is
pretty
accurate.
500 - 100 = 400
Step 1:
Rounding is
always first.
Decide which
place to round to.
Step 2:
Round each
number to
the hundreds
place.
© 2007 M. Tallman
Step 3:
Now you can
subtract 100
from 500,
mentally.
Rounding Tip: The
lower the place, the
more accurate the
answer. However, if
you round too low,
your problem may be
more difficult to
solve.
5,251 - 896
Rounding Tip: The
higher the place,
the easier your
problem will be to
solve. However,
your answer may not
be as accurate.
5,000 - 900 = 4,100
The actual answer is 4,355, so
our estimation is pretty accurate
Step 1:
Rounding is
always first.
Decide which
place to round to.
Step 2:
Round the first addend
to the thousands place
and the second addend
to the hundreds place.
© 2007 M. Tallman
Step 3:
Now you can
subtract 900
from 5,000,
mentally.
52,187 - 18,978
The actual
answer is
33,209, so our
estimation is
pretty
accurate.
50,000 - 20,000 = 30,000
Step 1:
Rounding is
always first.
Decide which
place to round to.
Step 2:
Round each
addend to the
ten thousands
place.
© 2007 M. Tallman
Step 3:
Now you can
subtract 20,000
from 50,000,
mentally.
$19.67 - $6.35
The actual
answer is
$13.32, so our
estimation is
pretty
accurate.
$20.00 - $6.00 = $14.00
Step 1:
Rounding is
always first.
Decide which
place to round to.
Step 2:
Round $19.67 to the
nearest ten dollars.
Round $6.35 to the
nearest dollar.
© 2007 M. Tallman
Step 3:
Now you can
subtract $6.00
from $20.00,
mentally.
Estimate Each Difference
1. $21.89 - $6.78
$20.00 - $7.00 = $13.00
2. 467 - 221
500 - 200 = 300
3. 745 - 467
700 - 500 = 200
4. 4,897 - 898
5,000 - 900 = 4,100
© 2007 M. Tallman
Estimate Each Difference
5. 897,965 - 12,854
900,000 - 10,000 = 890,000
6. $47.90 - $27.87
$50.00 - $30.00 = $20.00
7. 5,897 - 4,465
6,000 - 4,000 = 2,000
8. 765,987 - 46,980
800,000 - 50,000 = 750,000
© 2007 M. Tallman
Estimate Each Difference
9. $8.75 - $3.98
$9.00 - $4.00 = $5.00
10. $776.98 - $547.98
$700.00 - $500.00 = $200.00
11. 8,321 - 3,432
8,000 - 3,000 = 5,000
12. 667,876 - 446,987
700,000 - 400,000 = 300,000
© 2007 M. Tallman