Transcript Estimate Sums

© 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.
5,346
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
5,346
Just
Ignore!
3 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.
3,576
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.
3, 5
676
00
5+1=6
7 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
486 + 130
The actual
answer is 616, so
our estimation is
pretty accurate.
500 + 100 = 600
Step 1:
Rounding is
always first.
Decide which
place to round to.
Step 2:
Round each
addend to
the hundreds
place.
© 2007 M. Tallman
Step 3:
Now you can
add 500 and
100
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.
5,387 + 386
Rounding Tip: The
higher the place,
the easier your
problem will be to
solve. However,
your answer may not
be as accurate.
5,000 + 400 = 5,400
The actual answer is 5,773, 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
add 5,000
and 400
mentally.
5,387 + 386
5,000
5,400 + 400 = 5,800
5,400
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
add 5,400
and 400
mentally.
44,897 + 26,578
The actual
answer is 71,475,
so our estimation
is pretty
accurate.
40,000 + 30,000 = 70,000
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
add 40,000
and 30,000
mentally.
$8.67 + $6.75
The actual
answer is $15.42,
so our estimation
is pretty
accurate.
$9.00 + $7.00 = $16.00
Step 1:
Rounding is
always first.
Decide which
place to round to.
Step 2:
Round each
addend to
the nearest
dollar.
© 2007 M. Tallman
Step 3:
Now you can
add $9.00
and $7.00,
mentally.
Estimate Each Sum
1. $21.89 + $6.78
$20.00 + $7.00 = $27.00
2. 467 + 721
500 + 700 = 1,200
3. 145 + 467
100 + 500 = 600
4. 4,897 + 598
5,000 + 600 = 5,600
© 2007 M. Tallman
Estimate Each Sum
5. 897,965 + 12,854
900,000 + 10,000 = 910,000
6. $47.90 + $271.87
$50.00 + $300.00 = $350.00
7. 5,897 + 4,465
6,000 + 4,000 = 10,000
8. 765,987 + 46,980
800,000 + 50,000 = 850,000
© 2007 M. Tallman
Estimate Each Sum
9. $8.75 + $3.98
$9.00 + $4.00 = $13.00
10. $376.98 + $547.98
$400.00 + $500.00 = $900.00
11. 8,321 + 32,432
8,000 + 30,000 = 38,000
12. 167,876 + 446,987
200,000 + 400,000 = 600,000
© 2007 M. Tallman