Question

I need help finding the volume of this pentagonal pyramid !!!

Answer 1

whatcha stuck on?

Answer 2

First of all , is there anyway I can draw a picture on here to make it easier?

Answer 3

lol ... not that I have found

Answer 4

there is an attach file button here, but it is nnew. might allow you to post a pic tho

Answer 5

ehh, nahh. i'll just attempt to explain. okay so each side of the base has a length of 16 cm. Then the base has a annulus of 11. And it looks like the height is 36 cm

Answer 6

annulus; thats a term I aint familiar with.. can you explain it?

Answer 7

a washer shape

Answer 8

it's the length from the center of the shape to the middle of the edge of the side

Answer 9

circular disk with a hole missing from the center

Answer 10

maybe i'm not using the right term

Answer 11

ahhh; it looks like we could find the rea of on section of it by using the base and the height and the side length to help us

Answer 12

my keyboard hates me....

Answer 13

lol

Answer 14

so how do we do it

Answer 15

what methods do we know? is this calculus or something else?

Answer 16

geometry. . . lol

Answer 17

so we have a right triangle that forms the base and height, we have a width of ....whatever a side was all the way to 0 at the tip....

Answer 18

okay. here, can u wait a minute im gonna try to draw a picture of it and attach the file

Answer 19

http://www.mathsisfun.com/geometry/pentagonal-pyramid.html

gives us the volume as:

1/3 [base area] times height

Answer 20

yes i know that.

Answer 21

And area of pent is: (length of 1 side)^2 x 1.7

Answer 22

what is a pent

Answer 23

Area = 16^2(1.7)(36)/3 is what it looks to be.

pentagon

Answer 24

oh. ha. okay. so you took 16 to the second power , but where did u get 1.7?

Answer 25

1.7 is what someone smarter than me got when they figured out the formula for the area of a pentagon :)

s^2(1.7) = area of pentagon

Answer 26

the teacher gave us the answers because this a review for a test on monday. and she said the answer should be 5260. i just wanna see how she got there so i can do it on the test

Answer 27

okay... i think. lol

Answer 28

i meant 5280cm3. my bad

Answer 29

I get 5222.4 but is close enough to account for rounding and such

Answer 30

when we chop of decimals; we skew the answers... so it all depends on how it was calculated..

Answer 31

yeah. okay and explain to me where you got 36 please

Answer 32

you said the height was 36.

(1/3) (base area) (height)

base area = (side^2)(1.7)

Answer 33

ohhh wow. duhh. sorry. brain fart lol

Answer 34

:)

Answer 35

do you remember that you asked about the volume of a pentagonal pyramid :) time passed and we got to here :)

Answer 36

ha , yes. okay that works.

Answer 37

do you have time for some more questions?

Answer 38

fraid not, library closes in 10 minutes and my internet goes with it... but have a great day :)

Answer 39

okay thank you! you too!