3rd Grade Rounding NBT.1

Symbols

I do: My turn to talk. This is the explanation section of our
lesson, where you are required to listen.

We do: This is where we discuss or work on the concepts
together.

You do: Your turn to be involved. You may be working in a
group or on an activity individually.

What Is Rounding?

Rounding is one way to simplify numbers so they are easier to work
with.
You might roundnumbers when performing a particular addition
strategy or when working with money.
It is a very helpful skill to learn, so let’s get started.

Rounding Up or
Rounding Down?

0

1

2

3

4

5

6

7

8

9

Rounding Up or Down?

When it comes to rounding numbers, we
need to know which digits will round up
and which will round down.
This special “Round-o-Matic” machine
will round up a digit if it is large enough
to hit the bell. Otherwise, it will round it
down.
Let’s test the machine with 7.

7 rounds up!

0

1

2

3

4

5

6

7

8

9

7

Rounding Up or Down?

Let’s test the other digits! One at a time,
click on each button below to see if it will
round up or round down.

0

1

2

3

4

5

6

7

8

9

5

0

1

2

3

4

5

6

7

8

9

6

8

9

1

2

3

4

Next

0

What Do You Notice?

What do you notice about the digits that will round down and the digits
that will round up? Why did the machine not work for zero?

0

1

2

3

4

5

6

7

8

9

0

1

2

3

4

5

6

7

8

9

Rounding to the Nearest Ten

Rounding Down to the Nearest Ten

When rounding numbers, we need to
know what nearest value we are
rounding to.
For example, round 53 to the nearest
ten.
1.

Start by locating the digit in the tens
column.

2.

Move one column to the right.

3.

Look at the digit in the ones
column.

53

tens

ones

012
3

Rounding Down to the Nearest Ten

4.

Determine if the digit will make the
number round up or down.

5.

We know that a 3 will round down.

6.

Round the 3 down to a 0.

7.

53 rounded to the nearest ten is 50. 5

tens

ones

Rounding Up to the Nearest Ten

We now know how to round down.
Let’s round a number up to the nearest
ten.
For example, round 38 to the nearest
ten.
1.

Start by finding the digit in the tens
column.

2.

Move one column to the right.

3.

Look at the digit in the ones
column.

38

tens

ones

3

09
8

4

Rounding Up to the Nearest Ten

4.

We know that an 8 will round up.

5.

Round the 8 up to the next group of
ten.

6.

38 rounded to the nearest ten is 40.

tens

ones

Rounding to the Nearest Ten

Let’s look at these numbers
and determine whether
the number will round up
or round down to the
nearest ten.
Click the correct word
below each number. It will
animate into position if
correct.

79

or

or12

or64

145

or

Next

Rounding to the Nearest Ten

Let’s work together to round these numbers to the nearest ten.

Answers

Use the pen tool to write on the slide. Press Esc to stop using the pen tool.

47

18

33

96

122

Rounding to the Nearest Ten

Now it’s your turn. In your notebook, round the following numbers to
the nearest ten.

63

55

76

132

107

Answers

Match

Match the following Round to the nearest Ten

• 63

• 55

• 76

• 132

• 107

60

60

80

130

110

• 60

• 60

• 80

• 130

• 110

Rounding Within
Larger Numbers

Rounding Within Larger Numbers

When rounding larger numbers, it is important to know each digit’s
place value. Let’s look at rounding the following number.

3,629

Rounding Within Larger Numbers

Round, 3,264 to the nearest
hundred.
1.

Split the number into its place
value columns.

2.

Find the digit in the hundreds
column.

3.

Move one column to the right
(a lesser value column).
3629

tens

ones

hundreds

thousands

9
8
7
6
5
4
3
2
1
0

2
1
0

Rounding Within Larger Numbers

4.

Determine if this digit will
round the number up or down.

Note: It does not matter what the digits are in
the lesser value columns further to the right.
5.

We know that a 2 will make the
number round down.

6.

We round the 2 and all
columns to the right, down to a
zero.
36

tens

ones

hundreds

thousands

29

2
1
0

9
8
7
6
5
4
3
2
1
0

Rounding Within Larger Numbers

7.

3,629 rounded to the nearest
hundred is 3,600.

36

tens

ones

hundreds

thousands

,

Rounding Within Numbers

Let’s work together to round these numbers to the given multiple of ten.

Answers

Use the pen tool to write on the slide. Press Esc to stop using the pen tool.

186

1,209 2,354

364

8,479

to the nearest 10

to the nearest 100

to the nearest 100

to the nearest 10

to the nearest 100

Rounding Within Larger Numbers – Answers

186

1,209 2,354

364

8,479

190

1,200 2,400

360

8,500

to the nearest 10

to the nearest 100

to the nearest 100

to the nearest 10

to the nearest 100

Rounding Within Larger Numbers

Now it’s your turn. In your notebook, round the following numbers as
indicated.

Answers

253

2,380 1,151

556

6,083

to the nearest 10

to the nearest 100

to the nearest 100

to the nearest 10

to the nearest 100

Match

Match the following Round to nearest ten and hundred

• 250

• 2,380

• 1,151

• 556

• 6,083

253

2,400

1,200

560

6,100

• 253

• 2,400

• 1,200

• 560

• 6,100