1. 3,456.128 Good Afternoon! Today we will learn about
ROUNDING AND ESTIMATING DECIMALS
Do you remember Place Value position??? 3,

2. Let's review what we learned in the last lesson.
We learned that when we compare decimals, we line up the decimal points.
Then starting with the tenths place and working
from left to right, we find the first place that
the digits differ.

3. We use these symbols to compare
> greater than
< less than
= equals
We can also plot decimals on a number line.

4. And finally.....
If the number of decimal places is not the same for
the 2 numbers, we must add "place holding" zeros.
Then, we can line up the decimals and compare.
Terrific! Let's move on to the new lesson

5. In order to round decimals, we first need
to underline the digit to be rounded.
83.64
For example, if we are to round to the nearest
tenth, we underline the digit in the tenths place.

6. * * The second step is to look at the digit TO THE RIGHT OF
the underlined digit.
83.64
Look here! *
If the digit is 4 or less, the underlined digit remains the same. *
If the digit is 5 or more, we add 1 to the underlined digit.

7. Therefore, if we round 83.64 to the nearest tenth, we get.............
(Keep it the same)

8. . On a number line, we can see that 83.64 is closer to
83.6 than it is to 83.7. .
83.61
83.62
83.63
83.6
83.64
83.65
83.66
83.67
83.68
83.69
83.7

9. 40.458 Let's try another..... Round 40.458 to the nearest hundredth.
Underline the digit in the hundredths place.
40.458

10. 40.458 * * The second step is to look at the digit TO THE RIGHT OF
Look here!
The second step is to look at the digit
TO THE RIGHT OF
the underlined digit. *
If the digit is 4 or less, the underlined digit remains the same. *
If the digit is 5 or more, we add 1 to the underlined digit.

11. 40.458 40.46 In this case, the digit to the right of the
underlined digit is greater than 5 so
we add 1 to the underlined digit to round to
the hundredths place.
40.46

12. If we want to round to the nearest WHOLE NUMBER...
we first must underline the digit in the ones place.
For example, let's round to the nearest
WHOLE NUMBER.

13. 146.75 * * We underline the digit in the ones place.
Look here!
We underline the digit in the ones place.
And, once again, we look at the digit to the right
of the underlined digit. *
If the digit is 4 or less, the underlined digit remains the same. *
If the digit is 5 or more, we add 1 to the underlined digit.

14. 147 146.75 Therefore, if we round 146.75 to the nearest
So, in this case, we add 1 to the underlined digit.
Therefore, if we round to the nearest
whole number, we get
147

15. . On a number line, we can see that 146.75 is
closer to 147 than it is to 146. .
146.00
146.25
146.50
147.00
146.75

16. Now, let's round 14.97 to the nearest tenths place.
Look here!
Underline the digit in the tenths place and once
again, look at the digit to the right. *
If the digit is 4 or less, the underlined digit remains the same. *
If the digit is 5 or more, we add 1 to the underlined digit.

17. 14.97 14.97 15.0 HOWEVER, when we add 1 to the 9, we get 10
In this case, the number 7 is greater than 5 so we
have to add 1 to the underlined digit.
HOWEVER, when we add 1 to the 9, we get 10
so we change the 9 to a 0 AND add 1 to the 4 as well.
14.97
Change to 5
Change to 0
15.0
If we round to the nearest tenths place, we get

18. . On a number line we can see that 14.97 is closer
to 15.0 than to 14.9. .
14.9
14.91
14.92
14.93
14.94
14.95
14.96
14.97
14.98
14.99
15.0

19. Let's practice.... 1.) Round to the nearest tenth. 65.76
2.) Round to the nearest whole number
3.) Round to the nearest hundredth
4.) Round to the nearest tenth
5.) Round to the nearest hundredth

20. For example, if we purchase 4 items at the store
We often use ESTIMATION when we want
to approximate a reasonable sum or difference.
For example, if we purchase 4 items at the store
that cost $3.98, $6.08, $2.85, and $
we can estimate the sum by rounding to the
nearest whole dollar.

21. We estimate that our purchase will cost about $14.00
round to
$3.98
$6.08
$2.85
$1.25
$4.00
$6.00
$3.00
$1.00
$14.00
We estimate that our purchase will cost about
$14.00

22. We can estimate by rounding.....
It is easy to add or subtract decimals
when we round to the nearest whole number.
EXAMPLE: = ?
We can estimate by rounding.....
= 19

23. 4.2 + 1.76 = 7.8 + 1.126 = 12.1 - 7.05 = Let's practice a few.....
Estimate: = = =

24. BREAK

25. GAME

26. 1.) Write three different decimals
that round to 12.0 when rounded
to the nearest tenth.

27. 2.) Can you round this decimal to the
nearest thousandth?

28. 3.) How many numbers are there that
round to 67.45?

29. Assessment
1.) Round to the nearest tenth
2.) Round to the nearest hundredth
3.) Round to the nearest whole number
4.) Round to the nearest thousandth
5.) Round to the nearest tenth

30. 6.) Estimate: =
7.) Estimate: =
8.) Estimate: =
9.) Estimate: =
10.) Estimate: =

31. 1. 2. * * In order to round decimals, we first need
You did a wonderful job today!
Let's review what we learned. 1.
In order to round decimals, we first need
to underline the digit to be rounded. 2.
The second step is to look at the digit
TO THE RIGHT OF the underlined digit. *
If the digit is 4 or less, the underlined digit remains the same. *
If the digit is 5 or more, we add 1 to the underlined digit.

32. If the underlined digit is a 9 and we need
to round it "UP", we change the 9 to a 0 and add
1 to the digit to the LEFT of 9.
Example: Round 4.98 to the tenths place.
5.0
We often use ESTIMATION when we want
to approximate a reasonable sum or difference.
We can ESTIMATE by rounding to the nearest
whole number.

33. You worked hard today!
Congratulations!!!