don steward
mathematics teaching 10 ~ 16

Saturday, 18 December 2010

trapezium bit ares

a trapezium (trapezoid)

why are the areas of the purple (left) and orange (right) triangles the same?

if the bottom (base) of the trapezium is double the length of the top,
what can be said about the areas of the yellow and the maroon triangles?

so, what fraction of the whole trapezium area is the yellow triangle?

in general, if the bottom length is 'k' times longer than the top length,
show that the purple and orange triangles are (each) k  x  area of the yellow triangle.

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