Dividing Decimals

1
Dividing Decimals
Section 5.4
2
Division of decimal numbers is similar to
division of whole numbers.
The only difference is the placement of a decimal
point in the quotient. If the divisor is a whole
number, divide as for whole numbers then place
the decimal point in the quotient directly above
the decimal point in the dividend.
8
0
4
- 5 0 4
2 5
2
-2 52
0
3
If the divisor is not a whole number, we need to
move the decimal point to the right until the
divisor is a whole number before we divide.
8
4
- 504
25
2
-252
0
Martin-Gay, Prealgebra, 5ed
4
Dividing by a Decimal

• Step 1. Move the decimal point in the divisor to
  the right until the divisor is a whole number.
• Step 2. Move the decimal point in the dividend
  to the right the same number of places as the
  decimal point was moved in Step 1.
• Step 3. Divide. Place the decimal point in the
  quotient directly over the moved decimal point in
  the dividend.

Martin-Gay, Prealgebra, 5ed
5
Estimating When Dividing Decimals
Divide 258.3 2.8
Exact
Estimate
rounds to
Martin-Gay, Prealgebra, 5ed
6
There are patterns that occur when dividing by
powers of 10, such as 10, 100, 1000, and so on.
The decimal point moved 1 place to the left.
The decimal point moved 3 places to the left.
The pattern suggests the following rule.
Martin-Gay, Prealgebra, 5ed
7
Dividing Decimals by Powers of 10 such as 10,
100, or 1000, . . .
Move the decimal point of the dividend to the
left the same number of places as there are zeros
in the power of 10.