Odometers and the Place Value Chart

Bronson-Cochran, Donna               George B. Swift         
                                     (312) 989-3795
                           

Objectives:
To add decimals with the use of the odometer; To place given numbers 
on the place value chart; To add numbers to the millionths on the 
calculator.   

Apparatus needed:
Place value chart, calculators, overhead projector, projection 
calculator, lightweight cardboard, cutting instrument (scissors and 
single-edge razor blades), masking tape or scotch tape, pencils, 
straight edge and markers.

Strategies:
Students will begin to make odometers by cutting five rectangular 
shaped holes out of a piece of lightweight cardboard.  Another long 
strip of card board can be taped to the back at each end of the strip. 
Now students are to make narrow strips (one strip for each hole cut) 
with the digits 0 through 9 written on them, spaced at even intervals.  
These are then looped behind the cardboard strip on the large card.  
The digits should then be able to show through the windows.  Students 
can locate the decimal point to show tenths, then label the "odometer" 
to indicate kilometers. 

To add 58.2 km and 63.9 km, one first registers 58.2 on the odometer, 
then turns the tenths loop nine units.  When a zero is reached in the 
tenths window, the ones are increased by 1 just as an odometer in a 
car would function.  The student works successively from right to 
left, increasing the ones column by 3, and tens column by 6, 
remembering that when a zero is reached in a column it should trigger 
an increase in the column to the left.  Students should practice 
several problems using the odometer. 

Activities
For this activity you will need a place value chart.  The chart could 
be purchased or you could make one yourself.  If you decide to make the 
chart it can be extended to include as many decimal places as you 
need.  You will have many examples of number like sixty-seven and four 
thousand two hundred fifty-one millionth, seventy and one hundred 
twenty-twenty-three thousandths.  Each number will be written on a card 
and the students should be able to place them correctly on the place 
value chart. 

Another activity that could be used is working with the projection 
calculator.  Students should use their calculators to add decimals. 
Example 258.009878 + 009.787 + 89.1949 +.78     
You will do the same problem using the projection calculator and the 
overhead projector.