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What is a simple formula for finding the volume of a triangular pyramid with a base side length of 18 and a height of 4?

 

please hurry!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 May 13, 2014

Best Answer 

 #6
avatar+36 
+8

What are ALL the dimentions?

 May 13, 2014
 #1
avatar
0

wet der herck. im gonna fail my math homework!!!!

 May 13, 2014
 #2
avatar+36 
0

V=Bh

So it would be the area of the base times the heighth. I think the answer is 72units^2

 May 13, 2014
 #3
avatar+36 
0

NO 72units^3 sorry

 May 13, 2014
 #4
avatar+1006 
0

@cdromdj: You second answer (the more recent one) seems to be correct, since we are finding volume.

 May 13, 2014
 #5
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0

wat. i got 240 and the online calculator got 120.

 May 13, 2014
 #6
avatar+36 
+8
Best Answer

What are ALL the dimentions?

cdromdj May 13, 2014
 #7
avatar+130466 
+5

The "formula" is .......  (1/3) * (Area of the base)  * (Height)

The height is easy.

The area of the base is a little more complicated.

It's given by (√(3)/4)(s2), where s is the side length of the pyramid.

So we have  (1/3) * (√(3)/4)(182) * (4) = (1/√(3))(324) = (324 / √(3)) ≈ 187.06 cubic units

 May 13, 2014
 #8
avatar+36 
0

What  CPhill said

 May 13, 2014
 #9
avatar+118703 
+5

I think CPhill has assumed that the base is an equilateral triangle of side length 18 units.

This is not actually stated in the question but i guess it is a reasonable assumption.

All the angels are 60 degrees

----------------------

in triangle ABC 

 Area=12×a×b×sinC

Area=12×18×18×sin60

Area=162×32

Area=81×3

---------------------------------------

Volume=13×Area×height

Volume=13×81×3×4

Volume=108×3    units cubed.   

Volume187unit3

 May 13, 2014

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