Author Topic: basic math help  (Read 867 times)

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OK, I'm studying for an exam and me and the answer-booklet don't agree. Please help me.

There is a piramid, PQRS T with PQ=QR=RS=PS=6 and height=8.
There is a cube thingy in this piramid, ABCDEFGH. A B C and D are in the middelpoints of PT, QT, RT and ST. A B C and D are in the groundsquare of the piramid.

Calculate the volume inside the piramide but outside the cube.

I get the following:
Volume(piramid)=1/3*6*6*8=96
Volume(cuboid)=3*3*4=36
Volume(piramid-cuboid)=96-36=60.

The answer, according to the booklet, is 36. What's wrong here?
« Last Edit: December 19, 2004, 08:46:10 am by 936 »
just another newbie without any modding, FREDding or real programming experience

you haven't learned masochism until you've tried to read a Microsoft help file.  -- Goober5000
I've got 2 drug-addict syblings and one alcoholic whore. And I'm a ****ing sociopath --an0n
You cannot defeat Windows through strength alone. Only patience, a lot of good luck, and a sledgehammer will do the job. --StratComm

 

Offline Setekh

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The volume of the pyramid is right. Either your solution for the cube is the problem, or the answer is indeed wrong. Knowing that, I'm still unsure about the cube thingy. Need some more information about EFGH... because if I've drawn this diagram correctly, if ABCD is the base of the cube, then most of the cube is not actually inside the pyramid. :nervous:
- Eddie Kent Woo, Setekh, Steak (of Steaks), AWACS. Seriously, just pick one.
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ABCD is the base of the cube. You create ABCD by drawing a line straight down from the middelpoints of the ribs of the piramid.

EDIT: Here are the answers, mind, it's a big PDF. It's question 1b.

http://www.getalenruimte.epn.nl/getalenruimte_editie1998/ContentLeerling/vwoNGNT3/1/x_Hele_hoofdstuk/2_Uitwerking_algemene_herhaling/1_antwoorden.pdf

The diagrams of 1a are of the thing we're talking about.
« Last Edit: December 19, 2004, 08:43:48 am by 936 »
just another newbie without any modding, FREDding or real programming experience

you haven't learned masochism until you've tried to read a Microsoft help file.  -- Goober5000
I've got 2 drug-addict syblings and one alcoholic whore. And I'm a ****ing sociopath --an0n
You cannot defeat Windows through strength alone. Only patience, a lot of good luck, and a sledgehammer will do the job. --StratComm

 

Offline Setekh

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But is T the apex of the pyramid? In that case, that would make A,B,C,D the midpoints of PT, QT, RT, ST (the "ribs" of the pyramid) - is that more accurate than your description above?
- Eddie Kent Woo, Setekh, Steak (of Steaks), AWACS. Seriously, just pick one.
HARD LIGHT PRODUCTIONS, now V3.0. Bringing Modders Together since January 2001.
THE HARD LIGHT ARRAY. Always makes you say wow.

 
Oh, I just can't friggin type, can I?

You're right. I should learn how to type.
just another newbie without any modding, FREDding or real programming experience

you haven't learned masochism until you've tried to read a Microsoft help file.  -- Goober5000
I've got 2 drug-addict syblings and one alcoholic whore. And I'm a ****ing sociopath --an0n
You cannot defeat Windows through strength alone. Only patience, a lot of good luck, and a sledgehammer will do the job. --StratComm

 

Offline Setekh

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    • Hard Light Productions
That's okay. :)

Checking out their answer, they're definitely wrong. They've listed [(1/3)*6*6*8 - 3*3*4] as equal to [72-36]... when rather, it's [96-36], as you spotted earlier. You're correct.
- Eddie Kent Woo, Setekh, Steak (of Steaks), AWACS. Seriously, just pick one.
HARD LIGHT PRODUCTIONS, now V3.0. Bringing Modders Together since January 2001.
THE HARD LIGHT ARRAY. Always makes you say wow.

  
Thank you.


Now, I'm going to load up a truck full with fire-arms and off to that publisher. I'll be right back.
just another newbie without any modding, FREDding or real programming experience

you haven't learned masochism until you've tried to read a Microsoft help file.  -- Goober5000
I've got 2 drug-addict syblings and one alcoholic whore. And I'm a ****ing sociopath --an0n
You cannot defeat Windows through strength alone. Only patience, a lot of good luck, and a sledgehammer will do the job. --StratComm