The document discusses using compatible numbers when estimating division problems. Compatible numbers are numbers that contain a basic division fact, like 48 ÷ 8 = 6. The document provides examples of changing dividends and divisors to compatible numbers to estimate quotients. It explains a three step process: 1) look at the first numbers of the dividend and divisor, 2) find the closest basic fact, 3) use that fact to change the numbers and then divide to estimate the quotient.

1. © 2007 M. Tallman

2. © 2007 M. Tallman
When estimating division problems,
rounding will not work very well. You
must use compatible numbers.
Compatible numbers are numbers that
contain a basic division fact…
…8,100 ÷90, 720 ÷ 8, 144,000 ÷ 120

3. © 2007 M. Tallman
1. 120 ÷ 4
2.
3. 21,000 ÷ 7
4. 240 ÷ 6
5.
6.
7. 320 ÷ 8
8.
35,000
Find the compatible numbers in these division problems.
3,600
)
9
→ 12 ÷ 4
→ 36 ÷ 9
→ 21 ÷ 7
→ 24 ÷ 6
→ 42 ÷ 7
→ 35 ÷ 5
→ 32 ÷ 8
→ 96 ÷ 8
4,200
)
7
)
5
9,600
)
8

4. © 2007 M. Tallman
5
450
437 ÷ 9
9
÷ =
1
1
Step 1:
Look at the first couple
of numbers of the
dividend and the first
number of the divisor.
Step 2:
Find the closest
basic division
fact to these
numbers.
Step 3:
Use the basic fact to
change the dividend and
divisor in to compatible
numbers, and divide.
0
1 - 0 = 1
0
1 zero in the
quotient

5. © 2007 M. Tallman
7
490
508 ÷ 7
7
÷ =
1
1
Step 1:
Look at the first couple
of numbers of the
dividend and the first
number of the divisor.
Step 2:
Find the closest
basic division
fact to these
numbers.
Step 3:
Use the basic fact to
change the dividend and
divisor in to compatible
numbers, and divide.
0
1 - 0 = 1
0
1 zero in the
quotient

6. © 2007 M. Tallman
0
7 224
3
21
1
1
Step 1:
Look at the first couple
of numbers of the
dividend and the first
number of the divisor.
Step 2:
Find the closest
basic division
fact to these
numbers.
Step 3:
Use the basic fact to
change the dividend and
divisor in to compatible
numbers, and divide.
0
1 - 0 = 1
0
)
7)
1 zero in
the
quotient

7. © 2007 M. Tallman
7
4,20
4,324 ÷ 6
6
÷ =
1
1
Step 1:
Look at the first couple
of numbers of the
dividend and the first
number of the divisor.
Step 2:
Find the closest
basic division
fact to these
numbers
Step 3:
Use the basic fact to
change the dividend and
divisor in to compatible
numbers, and divide.
0
2 - 0 = 2
0
0
2
0
2
2 zeros in the
quotient

8. © 2007 M. Tallman
3,200
4 3,105
8
1
1
Step 1:
Look at the first couple
of numbers of the
dividend and the first
number of the divisor.
Step 2:
Find the closest
basic division
fact to these
numbers.
Step 3:
Use the basic fact to
change the dividend and
divisor in to compatible
numbers, and divide.
0
2 - 0 = 2
0
)
4)
0
2
2
2 zeros
in the
quotient

9. © 2007 M. Tallman
4,000
5 4,175
8
1
1
Step 1:
Look at the first couple
of numbers of the
dividend and the first
number of the divisor.
Step 2:
Find the closest
basic division
fact to these
numbers.
Step 3:
Use the basic fact to
change the dividend and
divisor in to compatible
numbers, and divide.
0
2 - 0 = 2
0
)
5)
0
2
2
2 zeros
in the
quotient
Tip: Do
not count
the zero
in 40.

10. © 2007 M. Tallman
Estimate 468 ÷ 8
Division Fact:_________
Estimate:____________
480 ÷ 8 = 80
48 ÷ 8 = 8

11. © 2007 M. Tallman
Estimate
Division Fact:_________
Estimate:____________
5,500 ÷ 5 = 1,100
55 ÷ 5 = 11
5,620 ÷ 5

12. © 2007 M. Tallman
Estimate
Division Fact:_________
Estimate:____________
2,000 ÷ 4 = 500
20 ÷ 4 = 5
2,198 ÷ 4

13. © 2007 M. Tallman
Estimate
Division Fact:_________
Estimate:____________
360 ÷ 12 = 30
36 ÷ 12 = 3
358 ÷ 12

14. © 2007 M. Tallman
Estimate
Division Fact:_________
Estimate:____________
1,800 ÷ 9 = 200
18 ÷ 9 = 2
1,976 ÷ 9