Rounding Whole Numbers and Decimals

1
Rounding Whole Numbers and Decimals

• Lesson 1-5

2

• You need to know your place values in order to
  round successfully.
• Lets revisit

3
The Units
The Thousands
The Millions
The Billions
The Thousandths
TENTHS
ONE
TEN
ONES
TENS
ONES
TENS
ONES
TENS
HUNDRED
HUNDREDTHS
HUNDREDS
HUNDREDS
HUNDREDS
The Decimals
The Whole Numbers
4
Rounding Whole Numbers
5
Underline the place value you need to round to.
Round 34,596 to the nearest thousands.
34,596.2
34,596.2
Thousands
6
Draw an arrow pointing to the number at the right
of the line.
34,596.2
7
Look at the number the arrow points to.
34,596.2
The arrow points to a FIVE.
8

• If the arrow is 0 through 4,
• leave the underlined number alone
• If the arrow 5 through 9
• add 1 to the underlined number

Since the arrow points to a five, you need to add
1 to the underlined number, 4. 4 1 5
34,596.2
9

• Copy all numbers to the left of the underlined
  number.
• Adjust the underlined number.
• Change all the numbers to the right of the
  underlined number into zeros.
• Drop all numbers after the decimal point.

34,596.2
35,000
Answer
10
Rounding Decimals
11
Underline the place value you need to round to.
Round 19.642 to the nearest hundredths.
19.642
19.642
hundredths
12
Draw an arrow pointing to the number at the right
of the line.
19.642
13
Look at the number the arrow points to.
19.642
The arrow points to a TWO.
14

• If the arrow is 0 through 4,
• leave the underlined number alone
• If the arrow 5 through 9
• add 1 to the underlined number

The arrow points to a 2. Since 2 is between 0 and
4, the underlined number, 4, stays the same.
19.642
15

• Copy all numbers to the left of the underlined
  number
• Adjust the underlined number as needed
• Do not write any numbers after the underlined
  number

The 2 comes after the decimal point. Drop it off.
19.642
19.64
Answer
16
What if I have to add one to the line, and my
underlined number is a 9?
17
Underline the place value you need to round to.
Round 39.993 to the nearest tenths.
39.993
39.993
tenths
18
Draw an arrow pointing to the number at the right
of the line.
39.993
19
Look at the number the arrow points to.
39.993
The arrow points to a NINE.
20

• If the arrow is 0 through 4,
• leave the underlined number alone
• If the arrow 5 through 9
• add 1 to the underlined number

The arrow points to a 9. Since 9 is between 5 and
9, you need to add a 1 to the underlined number,
9. 9 1 10
39.993
21

• Copy all numbers to the left of the underlined
  number.
• Adjust the underlined number as needed.
• Do not write any numbers after the underlined
  number.

1
1
39.993
1
.0
0
4
Answer
Dont forget to bring down the decimal point!
22
Here is a rhyme to help you remember rounding

• The arrows zero through four
• The line stays as before
• The arrows five through nine
• Add one to the line

23
Lets Practice
24
Round to the nearest tens
482.9984312
The answer is
480
8
25
Round to the nearest whole number(This means
round to the nearest ones)
62.5984312
The answer is
63
7
26
Round to the nearest tenth
805.5556
The answer is
805.6
6
27
Round to the nearest thousand.
45,789.59
The answer is
46,000
5
28
Round to the nearest hundred
59,623.54
The answer is
59,600
4
29
Round to the nearest thousandth
42.5984312
The answer is
42.598
3
30
Round to the nearest whole number
5.89436875
The answer is
6
2
31
Round to the nearest ten thousandth
92.5989312
The answer is
92.5989
Last