Asked by salma

a. half circle with a radius of 20 cm
b. half circle with a diameter of 3 ft
find the perimeter of each of the half circles.
i thought the answers were 12.42 ft for b and 165.6 cm for a, but i was told that i was wrong
Answered by Ms. Sue
a.
(3.14 * 40)/2 = ?

b.
(3.14 * 3)/2 = ?
Answered by salma
a. (3.14 * 40)/2 = 62.8
b. (3.14 * 3)/2 = 4.71
apparently that's still wrong
Answered by Ms. Sue
Oh -- I see what I did wrong. Sorry.

We need to add the diameter to the answer above.

62.8 + 40
4.71 + 3

Answered by Reiny
if r = 20 cm
arc of halfcircle = (1/2)(40)π = 20π
perimeter of halfcircle = 20π + 40 = appr 102.832 cm

if r = 3 ft
arc of halfcircle = (1/2)(6)π = 3π
perimeter of halfcircle = 3π + 6 = appr 15.425 ft
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