Lesson 3-4

Example 1  Divide Decimal by a Whole Number
Find 9.2  4.		

	4		Place the decimal point directly above the decimal point in the dividend.  
	  -8		Divide as with whole numbers.	
	    12
	  -12
	     0

9.2  4 = 2.3

Example 2  Real-World EXAMPLE
MOVIES  The cost for 5 teenagers to buy movie tickets is $23.75.  What is the cost for each ticket?

5		Place the decimal point directly above the decimal point in the dividend.  
   -20			Divide as with whole numbers.	
      37
    -35
       25
    - 25
        0

The cost for each movie ticket is $4.75.

Example 3  Divide a Decimal by a Decimal
Find 5.61  3.4.	Estimate   5.61  3.4 ≈ 6  3 or 2

To change the divisor to a whole number, multiply the divisor by 10.  You must also multiply the dividend by 10.  So, 5.61  3.4 becomes 56.1  34.

To change a whole number, multiply by 10.

Place the decimal point. Divide as with whole numbers 

Multiply by the same number, 10.

	34		 
    -34				
      221

Annex a zero and continue. 

    -204
       170
    - 170
          0

So, 5.61 3.4 is 1.65.		Check for Reasonableness   1.65 ≈ 2 

Example 4  Zeros in the Quotient and Dividend
Find 91.2  0.76.	Estimate   91.2  0.76 ≈ 91  1 = 91

To change a whole number, multiply by 100.

To change 0.76 to a whole number, multiply by 100.  Multiply 91.2 by the same number, 100.

Place the decimal point. Divide as with whole numbers 

Multiply by the same number, 100.

0.76	76		 
   	 - 76			

Write a zero in the ones place of the quotient since 0  76 = 0

      152
    - 152
          00
 
So, 91.2  0.76 is 120.	Check for Reasonableness  91 ≈ 120 

Example 5  Test EXAMPLE
GRIDDABLE   The Smith family purchased 2.4 gallons of apple cider for $4.44.  How much did they pay per gallon?

Read the Test Item
To find the price per gallon, divide the total cost by the number of gallons purchased.  

Solve the Test Item
To change the divisor to a whole number, multiply both the divisor and the dividend by 10.  So, 4.44  2.4 becomes 44.40  24.

1

8

5

24		  
   - 24				
      204
    - 192
        120
    -  120
           0

So, the Smith family paid $1.85 per gallon for the apple cider.