EPT
Quick help with Math
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rushz0rz
Canada5300 Posts
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yubee
United States3826 Posts
Also, the diameter of the sphere would be the hypotenuse of one side of the cube, wouldn't it? I dunno fuck geometry. geometryb is cool though. | ||
intrigue
Washington, D.C9935 Posts
edit: not trying to be a dick here but the second one is basic, basic basic basic geometry. please put some effort into this! | ||
alphafuzard
United States1610 Posts
On September 17 2008 14:57 yubee wrote: You're looking at the year the wrong way, I think. It's not the year 1982 that's important, but the difference between that year and the current year. Also, the diameter of the sphere would be the hypotenuse of one side of the cube, wouldn't it? I dunno fuck geometry. geometryb is cool though. not the hypotenuse but the space diagonal of the cube since the diameter is 12 cm which = the space diagonal = side length x root 3 thus the side length is 12/root 3 which simplified is 12 root3/root3 squared = 4 root 3 if you cant figure out the volume with the side length then leap off a bridge right now | ||
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EtherealDeath
United States8366 Posts
On September 17 2008 14:54 rushz0rz wrote: I have 2 problems due tomorrow and I suck severely at word problems like this. 1. If Old Uncle Tom were still alive he would be over 100 years old. He was x years old in the year x^2. Which birthday did he celebrate in 1982? Now I'm thinking it has to be in the form x^2 + x + 1982 or something? Or am I completely wrong? 2. A cube rests inside a sphere so that each vertex touches the sphere. If the inner radius of the sphere is 6cm, then what is the exact volume of the cube in cm^3? The opposite right angles would each be diameter, so 12cm? Ok hints only cause this should be ez... (actually I guess it depends on your year in school) 1) 1982 is importantish insofar as it gives you a convenient number to start experimenting with. In the end, it shouldn't be important, assuming I did the mental math correctly. Also assuming now is referring to 2008 and its not an old textbook (but that also shouldn't be important) Oh yea, there are many many answers btw lol. It's more entertaining if you assume Old Uncle Tom is Old Immortal Uncle Tom. :-) 2) Draw it out and it becomes very obvious. | ||
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rushz0rz
Canada5300 Posts
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HeavOnEarth
United States7087 Posts
The opposite right angles would each be diameter, so 12cm? ...problem CLEARLY states what is the exact volume of the cube in cm^3? just think about it lol | ||
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EtherealDeath
United States8366 Posts
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rushz0rz
Canada5300 Posts
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EtherealDeath
United States8366 Posts
And a variety of other answers. | ||
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HeavOnEarth
United States7087 Posts
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EtherealDeath
United States8366 Posts
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HeavOnEarth
United States7087 Posts
Hence cm x cm x cm = cm^3 here's a hint , the length , width and height of a cube, ARE ALL THE SAME shit O_o | ||
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rushz0rz
Canada5300 Posts
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EtherealDeath
United States8366 Posts
Of course my mental math is extremely inconsistent at this time of morning.... | ||
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EtherealDeath
United States8366 Posts
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HeavOnEarth
United States7087 Posts
define vertex and radius of spheeer. , i gave u formula for volume | ||
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EtherealDeath
United States8366 Posts
Of course you could be cute and calculate the volume of the cube directly from the radius of the circle, but that would be rote memorization :-D (Which has its purposes, everywhere :-o) | ||
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HeavOnEarth
United States7087 Posts
On September 17 2008 15:27 EtherealDeath wrote: Oh don't spoil the answer of 1728/(3sqrt(3)) HeavOnEarth ;-( Of course my mental math is extremely inconsistent at this time of morning.... oh i just do uh whatever that property of multiplication is called where instead of 144 x 12, you do ( 144 x 2 )+( 144x 10)= ~, 144 x 2 , 288 ,easy in head, 144 x 10, 1440, easy in head, so add them ... 1440 ...+ 288 = 1728, carry the one :p | ||
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HeavOnEarth
United States7087 Posts
On September 17 2008 15:27 rushz0rz wrote: so it is 12cm^3 ?? maybe im making it out to be more complicated than it actually is... QFT; but really i'm not patronizing you, i just want you to understand the basics around it, it's pretty hard if u don't get the big generalization (big picture) | ||
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rushz0rz
Canada5300 Posts
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EtherealDeath
United States8366 Posts
On September 17 2008 15:31 HeavOnEarth wrote: oh i just do uh whatever that property of multiplication is called where instead of 144 x 12, you do ( 144 x 2 )+( 144x 10)= ~, 144 x 2 , 288 ,easy in head, 144 x 10, 1440, easy in head, so add them ... 1440 ...+ 288 = 1728, carry the one :p Oh I just multiply it out cause it takes less than a second, at which point time is irrelevant. And it's not 1728, not the answer to the question anyways :-P | ||
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EtherealDeath
United States8366 Posts
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SayaSP
Laos5494 Posts
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HeavOnEarth
United States7087 Posts
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EtherealDeath
United States8366 Posts
On September 17 2008 15:38 SayaSP wrote: Isn't the formula for finding the diagonal like sqrt(3)*side That would be correct. But gotta let him find out why :-P | ||
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HeavOnEarth
United States7087 Posts
![[image loading]](http://i37.tinypic.com/bje5a8.jpg) | ||
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ketomai
United States2789 Posts
My advice, draw a picture. | ||
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geometryb
United States1249 Posts
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Nytefish
United Kingdom4282 Posts
 If you don't want to help then don't post. If you're just here to show off your (relatively) amazing Maths skills then go work in a nursery.For question one it's just trial and error. Starting with the 2nd statement and finding an 'x' that agrees with the first statement (and your common sense). ![[image loading]](http://www.mathaware.org/mam/00/master/essays/B3D/2/JPG/figure16.jpg) Using this picture and the fact that the longer diagonal is the diameter of the sphere, you can label a side (of the cube) 'x' and use some basic Pythagorus to find the longer diagonal in terms of x. | ||
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sigma_x
Australia285 Posts
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Nytefish
United Kingdom4282 Posts
I think assuming age is an integer is adequate, no need to be so "correct".  | ||
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