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# Help with this question

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Help with this question

Find the perimeter of each semicircle given its radius or diameter. (Round your answers to two decimal places.)

(a) d = 12 mm

_______ mm

(b) r = 4 ft

________ ft

(c)  9 m

___m

(d) 11.5 in

_____in

Sep 2, 2018

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The formula for perimeter/circumference is $$d\pi$$, where $$d$$ is the diameter.

a) $$d = 12$$, so the circumference is $$12\pi$$. Since the question is asking for a semicircle, we divide $$12\pi$$ by $$2$$ to get $$6\pi$$ mm. The question is asking to round your answer, so we can get $$18.85$$ mm.

b) If $$r = 4$$, then $$d = 8$$. We do the same thing for this problem as we did the last. The circumference for the semicircle would be $$4\pi$$ ft. This multiplied by $$\pi$$ rounds to $$12.57$$ ft.

c) The question does not specify is $$d = 9$$ or $$r = 9$$. If $$d = 9$$, the circumference would be $$4.5\pi$$ m. If $$r = 9$$, the circumference would be $$9\pi$$ m. This will give us $$28.27$$ m.

d) This question does not specify whether $$d = 11.5$$ or $$r = 11.5$$, as well. If $$d = 11.5$$, the circumference for the semicircle would be $$5.75\pi$$ in. If $$r = 11.5$$, the circumference for the semicircle would be $$11.5\pi$$ in. So our answer would be $$36.13$$ in.

- Daisy

Sep 2, 2018
edited by dierdurst  Sep 2, 2018
edited by dierdurst  Sep 2, 2018