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FILM AND EDUCATION
subtraction we undo what we do in addition. That is, in addition we make new ten-groups to combine with the tens we have at first. In subtraction we "unmake" or "break down" a ten group to help us to get ones enough to subtract.
Space does not permit detailed descriptions of activities which might be filmed to teach other mathematical understandings. Only outlines are given for other suggested activities.
The Inch, and its Divisions, as a Unit of Measure for Length
(Grades 4-5)
Picture the use or a yardstick in finding the heights of children. Show the relation of the foot ruler to the yardstick. Picture a boy making himself a foot ruler from a narrow strip of cardboard.
Picture the division into inches by copying from a ruler. Emphasize the fact that the one inch mark is not one inch. By movements, make clear that 1 inch, 2 inches, etc., are lengths and not marks.
For use in the 5th grade or above, the film might well picture the division of the inch into halves, quarters, and eighths.
After the half inch marks have been inserted, introduce the counting by halves with the pointing to each division mentioned, that is, count l/>, 1, 11/2, 2, 21/2, 3 etc. Count also thus, l/2, 2/2 or 1; 3/2 or U/2; 4/2 or 2; 5/2 or 2l/2.
After the quarter-inch marks have been inserted, introduce counting by fourths in the two ways suggested above. The same procedure may be followed after the eighth inch divisions have been made. Thus pupils are provided with basic experiences with whole numbers, improper fractions, and mixed numbers.
After the ruler has been completed, demonstrate the method of using it to measure to the nearest eighth of an inch.
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