Find the volume of a box that has a regular pentagonal base with sides measuring 7.3 inches and height of 15 inches. Round two decimal places

Question

Find the volume of a box that has a regular pentagonal base with sides measuring 7.3 inches and height of  15 inches. Round two decimal places

elisaneedshelp · Answer

@jigglypuff314

solomonzelman · Answer

You need to find the area of the pentagon base, and then multiply it times height.

Do you see why is that?

jigglypuff314 · Answer

area of regular pentagon = 0.25 root( 5 ( 5 + 2root(5)) ) (side^2)

jigglypuff314 · Answer

$$0.25\sqrt{5(5+2\sqrt{5}}~(side ^{2})$$

elisaneedshelp · Answer

this is what i have so far look

elisaneedshelp · Answer

my teacher wrote all these numbers in class and idk ?

jigglypuff314 · Answer

okay, she's doing it based on triangles...
a pentagon is made up of 5 equilateral triangles
erm...
area of equilateral triangle = 1/2  base (root(base^2-(1/2 base)^2 )
(I think?)

solomonzelman · Answer

a pentagon is made up of 5 equilateral triangles?|dw:1394455037184:dw|
I doubt that.

solomonzelman · Answer

you see what I mean, right?

elisaneedshelp · Answer

yes

jigglypuff314 · Answer

yeah ok, I don't know what I'm doing XP

solomonzelman · Answer

Pentagon with 3 equilateral triangles the 1 part,|dw:1394455145845:dw|

solomonzelman · Answer

My bad, you were right, @jigglypuff314m I am an retriceh...

|dw:1394455372534:dw|
|dw:1394455410337:dw|

solomonzelman · Answer

and the small divided triangles are each "30 60 90 triangles"

jigglypuff314 · Answer

now you're confusing me >,<
na I was wrong... if you divide it like that you get  54 degrees not 60

solomonzelman · Answer

I am not making a strait line accros in the middle, it's |dw:1394455625857:dw|