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Topic: Brick (Read 632 times) |
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regaleira
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One brick is one kilogram and half a brick heavy. How heavy is one brick?
This is another easy one! (but that´s why im posting it on easy and not on medium or hard) 
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ThudnBlunder
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The dewdrop slides into the shining Sea
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Re: Brick
« Reply #1 on: Jul 6th, 2005, 2:09pm » |
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on Jul 6th, 2005, 1:49pm, regaleira wrote:| One brick is one kilogram and half a brick heavy. How heavy is one brick? |
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on Jul 6th, 2005, 1:49pm, regaleira wrote:| This is another easy one! (but that´s why im posting it on easy and not on medium or hard) |
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Got any harder ones? 
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THE MEEK SHALL INHERIT THE EARTH.....................................................................er, if that's all right with the rest of you.
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JocK
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Re: Brick
« Reply #2 on: Jul 6th, 2005, 2:59pm » |
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Hmmm.. let's see. I got this far:
let's call the weight of a brick in kilograms "b".
With the help of my mathteacher we got close to a solution :
b = 1 + b/2
which can be re-arranged into:
b - 1 - b/2 = 0
Now if you try b =42 (always a good guess) you find:
42 - 1 - 42/2 = 42 - 1 - 21 = 22 =/= 0
Doesn't work...
But the following more advanced approach might work:
(I will hide this stuff so as not to give too much away !):
First we square both sides:
(b - 1 - b/2)^2 = 0
and take the exponent:
exp(b - 1 - b/2)^2 = 1
The solution to the problem can then be found by minimising
f(b) = (exp(b - 1 - b/2)^2 - 1)^2
I tried b = 42, but it still doesn't work....
A nasty problem. Any takers?
If not solvable analytically, would a Monte-Carlo simulation help? 
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| « Last Edit: Jul 6th, 2005, 3:03pm by JocK » |
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solving abstract problems is like sex: it may occasionally have some practical use, but that is not why we do it.
xy - y = x5 - y4 - y3 = 20; x>0, y>0.
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baddab457
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Posts: 51
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Re: Brick
« Reply #3 on: Jul 6th, 2005, 7:30pm » |
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did u think to far or did i not think far enough...
brick being b
there fore
b=1+b/2
2b=1
b=.5
i really need some sleep now though...
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"Dont Die For Your Country, Make Them SoB's Die For Theres" G Paton
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Icarus
wu::riddles Moderator
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Boldly going where even angels fear to tread.
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Re: Brick
« Reply #4 on: Jul 6th, 2005, 7:31pm » |
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Jock,
Were ever in one of my classes? I recall some approaches like this amongst my students work...
baddab457: Trust me - Jock is able to solve a simple equation. (Even if I was not familiar with his other posts, the very things he mentioned in this post would be enough to assure me of his ability to handle the equation here.) Therefore you may infer that he failed to solve this one on purpose.
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| « Last Edit: Jul 6th, 2005, 7:35pm by Icarus » |
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"Pi goes on and on and on ...
And e is just as cursed.
I wonder: Which is larger
When their digits are reversed? " - Anonymous
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honkyboy
Junior Member
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Posts: 101
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Re: Brick
« Reply #5 on: Jul 6th, 2005, 9:04pm » |
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Baddabs' answer still doesn't seem complete.
b=1/2 doesn't correctly solve the original equation.
First I will sove for the 'real' b. (br)
br= 1 + b/2 = 1+(1/2)/2=1.4
The weight of the brick (W) now is found if
br is subtituted back into the original equation using an unknown multiplier (N)
so . . .
W=N(1+br/2). substituting
W=N(1+1.4N/2) multiply by the squared reciprocal
W=20N-0.4N
W=19.6N
(I haven't figured how to solve for N yet. Icarus, would I get partial credit for this?)
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paul schmitz
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on Jul 6th, 2005, 7:30pm, baddab457 wrote:did u think to far or did i not think far enough...
brick being b
there fore
b=1+b/2
2b=1
b=.5
i really need some sleep now though...
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you guys are way overthinking. the answer is right here... almost. baddab just made a small error.
b = 1 + b/2
*2 (multiply every term by 2)
2b = 2 + b
-b
b = 2
if you think about it, you start with b = 1 + 1/2, then b = 3/2, so you plug it back in and now b = 1 + 3/4, b = 7/8. This is simply 1 + the sumation of [(1/2)^n], from n = 1 to n = infinity, which approaches 2 as n grows.
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otter
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Posts: 142
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Re: Brick
« Reply #7 on: Jul 13th, 2005, 11:52am » |
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on Jul 6th, 2005, 2:59pm, JocK wrote:Hmmm.. let's see. I got this far:
let's call the weight of a brick in kilograms "b".
...Much Deleted...
A nasty problem. Any takers?
If not solvable analytically, would a Monte-Carlo simulation help? |
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Perhaps if we restate the problem, the solution will become apparent:
0.999... brick is 0.999... kilograms and half a brick heavy. How heavy is 0.999... brick?
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We shall not cease from exploration. And the end of all our exploring will be to arrive where we started
and know the place for the first time.
T.S. Eliot
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xenon_nightmare
Newbie
Posts: 1
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Re: Brick
« Reply #8 on: Jul 13th, 2005, 12:39pm » |
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I believe one brick (now) is ~ 2 kilos 
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raprap
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Re: Brick
« Reply #9 on: Jul 15th, 2005, 4:13am » |
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Is it a regular masonry brick or a paver? They're different dimensions.
A masonry brick is 2 1/4x8 1/2 x 4 1/2 while a paver is normally 3x9x5 and that difference would definitely have an effect on the weight of a brick.
Rap
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