Question

3.
The volume of a cylinder is 980mc003-1.jpg in.3 The height of the cylinder is 20 in. What is the radius of the cylinder? (1 point)

7 in
49 in
327 in
18 in

Answer 1

whats the area of a circle?

Answer 2

umm idk thats y i need help on the question....

Answer 3

okay no problem, ill tell you, its \[\pi r^2\]

Answer 4

which is great so we have this we will call the area A, but what we really mean is \[\pi r^2\]

Answer 5

now lets build some walls, and really get a cylinder going!

Answer 6

so w now have this

Answer 7

what i have labeld L here is Height. what is the height of this cylinder?

Answer 8

20 inch

Answer 9

okay great lets put that in so i have divided the cylinder into lots of circles each is 1 inch thick

Answer 10

quick recap: whats the area of a circle?

Answer 11

this is supposed to be a QUICK recap :P

Answer 12

the area is πr2 lol

Answer 13

your damn right it is

Answer 14

so we know the area of 1 of these circles infact we know the area of every circle since they all have the same width, 1.

Answer 15

how many circles do we have stacked to make this cylinder?

Answer 16

5

Answer 17

sorry stupid website was being wierd

Answer 18

well, look at the side of the diagram, we know the area = pi r^2 when L = 1 ? yeah?

Answer 19

but in this example the height isnt 1, its 20! its 20 times 1.

Answer 20

so we need 20 circles stacked ontop of each other all with width 1, do you get that?

Answer 21

grr its sending my messages in random orders :(

Answer 22

do you follow so far?

Answer 23

well i wont be here when you get back, heres what you do. area = pi r^2, height = 20. Volume = area x height = pi r^2 times 20. you want to know the radius! so solve that equation for radius, solve:

\[V = \pi r^2 L\]

for r

Answer 24

then just put in your values for height = l and volume = v and you got the radius!

Answer 25

Idk what was happening I couldnt see the messages!!! well thankyou for ur help!!!! :)

Answer 26

yeah it decided to lag like crazy. did you solve it? and do you understand it!

Answer 27

its confusing but i get it, is the answer 7?

Answer 28

980mc003-1.jpg in.3 what does this mean in your question?

Answer 29

it stands for 980 πr inch 3

Answer 30

yeah 7 is good for me. Awesome. Give a girl the answer, she will solve the question, derive a girl the formula, and she can solve all the questions!

Answer 31

thankyou very much! :D

Answer 32

:) your welcome