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

- anonymous

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

- Stacey Warren - Expert brainly.com

Hey! We 've verified this expert answer for you, click below to unlock the details :)

- jamiebookeater

I got my questions answered at brainly.com in under 10 minutes. Go to brainly.com now for free help!

- amistre64

whatcha stuck on?

- anonymous

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

- amistre64

lol ... not that I have found

Looking for something else?

Not the answer you are looking for? Search for more explanations.

## More answers

- amistre64

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

- anonymous

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

- amistre64

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

- anonymous

a washer shape

- anonymous

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

- anonymous

circular disk with a hole missing from the center

- anonymous

maybe i'm not using the right term

- amistre64

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

- amistre64

my keyboard hates me....

- anonymous

lol

- anonymous

so how do we do it

- amistre64

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

- anonymous

geometry. . . lol

- amistre64

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....

- anonymous

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

- amistre64

http://www.mathsisfun.com/geometry/pentagonal-pyramid.html
gives us the volume as:
1/3 [base area] times height

- anonymous

yes i know that.

- amistre64

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

- anonymous

what is a pent

- amistre64

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

- anonymous

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

- anonymous

##### 1 Attachment

- amistre64

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

- anonymous

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

- anonymous

okay... i think. lol

- anonymous

i meant 5280cm3. my bad

- amistre64

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

- amistre64

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

- anonymous

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

- amistre64

you said the height was 36.
(1/3) (base area) (height)
base area = (side^2)(1.7)

- anonymous

ohhh wow. duhh. sorry. brain fart lol

- amistre64

:)

- amistre64

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

- anonymous

ha , yes. okay that works.

- anonymous

do you have time for some more questions?

- amistre64

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

- anonymous

okay thank you! you too!

Looking for something else?

Not the answer you are looking for? Search for more explanations.