Chapter 7 The Study Of Numbers Up To 20
think mathematically and manipulate numbers for a special purpose. The activity, consists in finding the total length of a handful of rods in the easiest way, and should be treated as a game: 1
Take a handful of rods. Put them end to end and find their total length. (Generally, the addition would be done indiscriminately and unsystematically.) Jumble them together again. Can you do it now without actually putting them end to end? Try this several times with different handfuls.
2 Take a new handful and try to arrange the rods in groups whose lengths add up to ten, and add them in this way by groups of ten. Now take other handfuls of rods and add their lengths by groups of ten; see if you can do it by just looking at them. Is it easier than the way you did it before? 3 Now take a handful of rods and put rods of the same color into groups and add them in this way. Take other handfuls of rods and, just by looking at them, add their lengths together by first adding rods of the same color together. Is this the easiest way? The answer given to this last question is not important. The purpose of the exercise is to make the pupils realize that there are alternative ways of adding a series of numbers. Once
Published on Nov 18, 2009