Transcript Rounding Power Point

Rounding
Objective:
•Round two-digit numbers to the nearest ten.
•Round three-digit numbers to the nearest hundred.
•Estimate sums and differences.
•Estimate products and quotients.
Vocabulary
•
•
•
•
•
•
•
•
Rounding
Approximately
Nearest
Hundreds
Place value
Differences
Almost
Close to
•
•
•
•
•
•
•
Estimation
About how many*
Tens
Thousands
Sums
Reasonable
Nearly
Rounding two-digit numbers
Two-digit number will be
rounded to the nearest ten.
26
So we can say that the
number 26 is closer to
30 than to 20.
30
RULES FOR ROUNDING
1.
Underline the number in the place
value you will round.
2. Look at the number to the right of the
underlined number.
3. If the number to the right is 0, 1, 2,
3, or 4, then the underlined number
stays the same.
4. If the number to the right is 5, 6, 7,
8, or 9, then the underlined number
needs to go up one more number.
5.
Every number to the right of the
underlined number becomes a zero.
Rounding three-digit numbers
Redondeando números de tres digitos
Three-digit number will be
rounded to the nearest
hundred.
520
500
So we can say that the
number 520 is closer to
500 than to 600.
RULES FOR ROUNDING
1.
Underline the number in the place
value you will round.
2. Look at the number to the right of the
underlined number.
3. If the number to the right is 0, 1, 2,
3, or 4, then the underlined number
stays the same.
4. If the number to the right is 5, 6, 7,
8, or 9, then the underlined number
needs to go up one more number.
5.
Every number to the right of the
underlined number becomes a zero.
26 is closer to 30 than to 20.
20
26
30
520 is closer to 500 than to 600.
500
520
600
Estimating sums
First, round all the numbers using the RULES FOR ROUNDING
Then, perform the operations.
12
+ 8
-------
10
+ 10
------20
Estimating differences
First, round all the numbers using the RULES FOR ROUNDING
Then, perform the operations.
25
- 11
-------
30
- 10
------20
RULES FOR ROUNDING
1. Underline the number in the place value you will
round.
2. Look at the number to the right of the underlined
number.
3. If the number to the right is 0, 1, 2, 3, or 4, then the
underlined number stays the same.
4. If the number to the right is 5, 6, 7, 8, or 9, then the
underlined number needs to go up one more
number.
5. Every number to the right of the underlined number
becomes a zero.
Review the vocabulary
•
•
•
•
•
•
•
•
Rounding
Approximately
Nearest
Hundreds
Place value
Differences
Almost
Close to
•
•
•
•
•
•
•
Estimation
About how many
Tens
Thousands
Sums
Reasonable
Nearly
Now you practice.
Round these numbers.
25
78
36
158
689
324
30
80
40
200
700
300
Practice rounding sums and differences
25
30
- 15
- 20
------------12
+ 36
-------
10
+ 40
-------
128
+ 42
-------
100
+ 40
-------
The cafeteria is selling ice cream cones for 23¢ and ice
cream sandwiches for 48¢. If Ms. Rodriguez buys an
ice cream cone and an ice cream sandwich, about how
much money will she spend?
$1.00
70 ¢
50 ¢
25 ¢