Areas of Similar Figures
Pacing:This lesson should take one class period
Goal:The purpose of this lesson is to connect similarity, areas, perimeters, and the scale factork.
Look Out!Students may get confused when attempting to set up a proportion regarding similar area. Areas have a
ratio ofk^2 , whereas perimeters have a ratio ofk. This may be a good time to review the fractionpreimage areaimage area =k
2
- Encourage students to use this proportion when referring to area.
Could There Be Giants? Before reading the section “Why There Are No 12’ Giants,” discuss Robert Wadlow,
the tallest man on record. The following website is the “official” Robert Wadlow information guide. Students are
captivated at Wadlow’s shoe size, his growth chart, and the photographs that can be found on this site. Encourage
students to further research people of great height and do quick summaries of their findings.
Gulliver’s Travels!Written by Jonathan Swift,Gulliver’sTravels tells of a man who visits two worlds, one where
people are 12 times his size (Brobdignagians), and another where people are 121 his size (Lilliputians). Use these
values forkto describe such things as the area of footprints.
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1.10. Perimeter and Area