Estimation of Irregular Surface Areas.

Bruce Hermsmeier
Middle School Math Teacher
La Mesa, California

Instructions: Have the students draw the outline of one of their hands in three different positions on a blank paper. The lines have to be continuous loops so have them connect the ends together at the wrist. You will notice immediately that many different sized shapes appear on each student's paper. (Something that would be hard to get them to do on their own.) Have the students shade in solid all the regions with area less than 1 square centimeter. Next have them shade in the regions with areas from 1 to 5 square centimeters with diagonal shading. (Here we have used .) The students are then instructed to shade the regions with areas from 5 to 10 square centimeters with dots. (Here we have used . Larger areas were left in my class but you could choose to color them otherwise.)
A nice feature of this exercise is that students can look at other student's work to compare and evaluate. I believe that this activity gives students a good understanding of what estimation is about as well as gain some judgement skills.

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