Transcript Compatible numbers

© 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
© 2007 M. Tallman
Find the compatible numbers in these division problems.
1. 120 ÷ 4
2. 9)3,600
3. 21,000 ÷ 7
4. 240 ÷ 6
5. 7) 4,200
6. 5)35,000
7. 320 ÷ 8
8. 8)9,600
© 2007 M. Tallman
→ 12 ÷ 4
→ 36 ÷ 9
→ 21 ÷ 7
→ 24 ÷ 6
→ 42 ÷ 7
→ 35 ÷ 5
→ 32 ÷ 8
→ 96 ÷ 8
437 ÷ 9
1 zero in the
quotient
1 - 0 = 1
1
0
1
450 ÷ 9 = 50
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.
© 2007 M. Tallman
Step 3:
Use the basic fact to
change the dividend and
divisor in to compatible
numbers, and divide.
508 ÷ 7
1 zero in the
quotient
1 - 0 = 1
1
0
1
490 ÷ 7 = 70
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.
© 2007 M. Tallman
Step 3:
Use the basic fact to
change the dividend and
divisor in to compatible
numbers, and divide.
7 ) 224
1 zero in
the
quotient
1
30
7 ) 210
1
0
Step 1:
Look at the first couple
of numbers of the
dividend and the first
number of the divisor.
1 - 0 = 1
Step 2:
Find the closest
basic division
fact to these
numbers.
© 2007 M. Tallman
Step 3:
Use the basic fact to
change the dividend and
divisor in to compatible
numbers, and divide.
4,324 ÷ 6
2 zeros in the
quotient
2 - 0 = 2
1 2
0
1 2
4,200 ÷ 6 = 700
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
© 2007 M. Tallman
Step 3:
Use the basic fact to
change the dividend and
divisor in to compatible
numbers, and divide.
4 ) 3,105
1 2
800
4 ) 3,200
1 2
2 zeros
in the
quotient
2 - 0 = 2
0
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.
© 2007 M. Tallman
Step 3:
Use the basic fact to
change the dividend and
divisor in to compatible
numbers, and divide.
Tip: Do
not count
the zero
in 40.
5 ) 4,175
1 2
800
5 ) 4,000
1 2
2 zeros
in the
quotient
2 - 0 = 2
0
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.
© 2007 M. Tallman
Step 3:
Use the basic fact to
change the dividend and
divisor in to compatible
numbers, and divide.
Estimate 468 ÷ 8
48
÷
8
=
8
Division Fact:_________
480
÷
8
=
80
Estimate:____________
© 2007 M. Tallman
Estimate 5,620 ÷ 5
55 ÷ 5 = 11
Division Fact:_________
5,500 ÷ 5 = 1,100
Estimate:____________
© 2007 M. Tallman
Estimate 2,198 ÷ 4
20 ÷ 4 = 5
Division Fact:_________
2,000 ÷ 4 = 500
Estimate:____________
© 2007 M. Tallman
Estimate 358 ÷ 12
36 ÷ 12 = 3
Division Fact:_________
360 ÷ 12 = 30
Estimate:____________
© 2007 M. Tallman
Estimate 1,976 ÷ 9
18 ÷ 9 = 2
Division Fact:_________
1,800 ÷ 9 = 200
Estimate:____________
© 2007 M. Tallman