Question

What is the circumference and area of a semi circle with a diameter of 20???? take pi=3.142

Answer 1

area of a circle is \[\pi r^2\]

Answer 2

so substitute in 20 for r

Answer 3

and then halve it because its a semi circle

Answer 4

20 is the diameter not the radius

Answer 5

oh yeah, then substitute r = 10

Answer 6

314.15???

Answer 7

did you do the halving step?

Answer 8

157......

Answer 9

thats correct, as an with your value of pi

Answer 10

what about circumference?

Answer 11

for the perimeter of the semicircle, you get the normal formula, \[2 \pi r\], substitute r = 10 and halve it. you then have to remember to add the length of the diameter, so add 20

Answer 12

31.4??

Answer 13

you have to add 20 for the base of the semi circle

Answer 14

why do you add the base?

Answer 15

why cant I just multiply the diameter 20 my 3.142??