Question

find the surface area
grapefruit with the circumfrace of 14

Answer 1

a grapefruit is going to ideally be a sphere; we need a formula for the surface area of a sphere

Answer 2

the radius value we can get from the circumference so it might be good to know the circumference of a circle formula as well

Answer 3

okay, so
C= 2 PI r
S.A.= 4 PI r ^2

Answer 4

good; now C = 14

14 = 2pi r ; therefore r = 14/7pi

plug that or some simplified version of r into the SA its good

Answer 5

okay so the rad. is 2 ? (my teacher said to round)

Answer 6

i was thinking 14/2 = 7 lol

Answer 7

14/2pi = r

Answer 8

oh!

Answer 9

okay good that makes more sence

Answer 10

so round 7pi and use that in SA

Answer 11

okay so i got 65 cm ^2
is that right?

Answer 12

id have to use a calculator ....

Answer 13

hmmm, can you? Becuase idk if i did it right?

Answer 14

62.38 or so depending on when you approximate

http://www.wolframalpha.com/input/?i=4*pi*%287%2Fpi%29%5E2

Answer 15

62.42 if you use 3.14 instead of pi

Answer 16

oh
so if i leave it in terms of PI?

Answer 17

nevermind

Answer 18

for accuracy yes; but you said you could round something or another

Answer 19

but 3.14 IS PI

Answer 20

no, 3.14159....... is pi

Answer 21

so its 62 :D

Answer 22

3.14 is an approximation for pi that they like to use in kindergarten classes :)

Answer 23

62 and a smidge yes

Answer 24

what about volume of a sphere? what is that formula?

Answer 25

just like SA resembles Circumference; Volume resembles the Area

V = 4/3 pi r^3