SOLUTION: Let ABCDEFGH be a rectangular prism, as shown, where AB = 2, AD = 3, and AE = 5. Find the volume of pyramid ACFH. https://latex.artofproblemsolving.com/0/a/3/0a3404805162de58ee7

Algebra ->  Volume -> SOLUTION: Let ABCDEFGH be a rectangular prism, as shown, where AB = 2, AD = 3, and AE = 5. Find the volume of pyramid ACFH. https://latex.artofproblemsolving.com/0/a/3/0a3404805162de58ee7      Log On


   



Question 1074800: Let ABCDEFGH be a rectangular prism, as shown, where AB = 2, AD = 3, and AE = 5. Find the volume of pyramid ACFH.
https://latex.artofproblemsolving.com/0/a/3/0a3404805162de58ee7c86ac6b0e5d23327c0026.png

Found 2 solutions by ikleyn, KMST:
Answer by ikleyn(53751) About Me  (Show Source):
You can put this solution on YOUR website!
.
Let ABCDEFGH be a rectangular prism, as shown, where AB = 2, AD = 3, and AE = 5. Find the volume of pyramid ACFH.
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The volume of our pyramid is equal to the volume of the rectangular prism minus the volumes of three OTHER pyramids 
that you can easily calculate:


V%5BACFH%5D = 2*3*5 - V%5BFAHE%5D - V%5BCABF%5D - V%5BCFGH%5D - V%5BCADH%5D - V%5BCADH%5D = 


      = 30 - %281%2F3%29%2A%281%2F2%29%2A5%2A3%2A2 - %281%2F3%29%2A%281%2F2%29%2A5%2A3%2A2 - %281%2F3%29%2A%281%2F2%29%2A5%2A3%2A2 - %281%2F3%29%2A%281%2F2%29%2A5%2A3%2A2 = 


      = 30 - %284%2F%283%2A2%29%29%2A5%2A3%2A2 = 30 - 20 = 10 cubic units.


Answer by KMST(5345) About Me  (Show Source):
You can put this solution on YOUR website!
The drawing looks (sort of) like this:

The prism has the diagonals of all its 6 faces marked.
Those diagonals split each rectangular face of the prism into two congruent right triangles,
with each of those triangles being half of a rectangular face of the prism.
Slicing along those diagonals,
they cut off 4 pyramids out of 4 corners of the prism,
to leave pyramid ACFH.
The volume of each of the pyramids cut off is 1%2F6 of the volume of the prism.
After removing 4%281%2F6%29=2%2F3 of the volume of the prism,
they are left with 1-2%2F3=1%2F3 of the volume of the prism.
Since the volume of the prism (in cubic units) is 2%2A3%2A5 ,
the volume left (the volume of ACFH) is
2%2A3%2A5%2F3=2%2A5=highlight%2810%29 .