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math question (1 Viewer)

Deem_Skills

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how did they get from the first step to the second? why are they squaring?
 

Drongoski

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Easy.

Area of smaller pentagon : area of larger pentagon = 4:25 =

.: side length of smaller pentagon : side length of larger pentagon = 2 : 5 [the regular pentagons being similar figures]

.: side length of smaller pentagon = (2/5)*22.5 cm = 9 cm

Note: the principle being simply: if A and B are similar figures, with length of one side of A being "a"
and the length of the corresponding side of B being 'b', then

area of A : area of B = square of 'a' : square of 'b'
.
 
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