Math CentralQuandaries & Queries


Question from John, a parent:

Piece of wire 72cm in length bent to make semicircle and diameter.Find
length of diameter.Answer given 28cm.How is this arrived at?Looked at
circumference in various ways but failed to understand how 28 cm was
arrived at.Thanks for the help.

For any radius, semicircle arc length = π r, diameter = 2 r.

Total = (2+π)r ~ 5.141592 r or roughly 36/7 r

If 36/7 r = 72cm, then r = 14cm, diameter = 28cm

Good Hunting!

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