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.
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