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# Brick

46 replies to this topic

### #21 Maxymus

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Posted 10 October 2007 - 04:48 PM

...if its one kilo and half of itself then...

This way of phrasing it inspired me to come up with another way of explaining why the answer is 2 kilos. I know why mathematically the algebraic solution works but like our infinite weight suggestion implies, perspective can change ones own truths. I shal try to explain this through a deductive reasoning as opposed to algebraic or Boolean expressions lol.

OK, here goes…now sit down, buckle up and pipe down lol…this is going to be bumpy :-D

One brick is one kilogram and half a brick heavy. What is the weight of one brick?

(a brick weighs 1 kilo and a half a brick) We know the brick weighs a minimum of 1 kilo right? And each half must weigh at least 1/2 kilo, right? So the minimum weight based on the information must be 1.5 kilos. It is impossible to have it any less than that.

But if the brick weighs a minimum, how do we figure out what the maximum is? We can work backwards using an arbitary answer to get some perspective and answer some questions. (Sometimes it helps to know an answer as to be able to ask the right questions even if the answer is wrong)

Take a brick that is 201 kilos. That is 200 + 1 kilo. A half of this brick is 100.5 kilos right? The problems states the weight is 1 kilo + half a brick. In this case half a brick is 100.5 + 1 and equals 101.5 This does not equal our arbitrary weight of 201 . So the brick at this point does not weight 201 for sure. You could try this with any other numbers and quickly you will see that the number seem to make more sense when they get smaller. So let’s try something smaller

Take a brick that is 4 kilos. (even number this time, much smaller). Half of this brick is 2 kilos right? The problems states the weight is 1 kilo + half a brick. In this case 2 + 1 equals 3 (oh so close but not quite) This does not match our entire weight. Aww..so sad. So needless to say we got closer the the numbers matching as they should but the brick does not weigh 4 kilos. Sorry , please play again !!.

Since 4 kilos was close and we know that the brick must weigh at least 1.5 kilos lets go a notch above that and make it 2 and see what happens. Take a brick that is 2 kilos. A half of this brick is 1 kilo right? (hehe see it coming yet?) The problems states the weight is 1 kilo + half a brick. In this case 1 kilos + 1 kilo equals 2 !! This fits our scenario perfectly. OMG DING DING DING DING DING YOU HAVE WON A TRIP TO THE FABULOUS ISLAND OF….. sike hehe.

Ok, guess that is all . I hope you had as much fun reading this as I had writing it. So many colors and textures in life to explore. I hope you all find time for yourselves to do just that.

Live in the NOW.
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Posted 19 October 2007 - 06:35 PM

i like the too (2) heavy answer

but mathematically you guys are all wrong everyone who says 1.5 kilograms needs to relearn algebra

if
1 Brick=1kg+.5Brick

subtract .5 brick from both side

.5Brick=1kg

1Brick=2kg

but the problem asks for the WEIGHT not the MASS so the answer is

F=MA

Weight is a force measured in Newtons

F=2kg*9.81 m/s^2

F=19.62 Newtons
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### #23 Fatone

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Posted 30 October 2007 - 06:09 PM

I think you guys are looking into this way too much. When you're trying to solve a riddle, just take the riddle for exactly what it says. Not "if" this and "if" that.

An old riddle is as follows: One brick is one kilogram and half a brick heavy.
What is the weight of one brick?

I know alot of you out there were saying "Well I read it as 1 brick is 1 kilogram and also half a brick". Truth is, an object cannot weight half of itself, so you're obviously reading the riddle wrong.

Others were saying "I read it as 1 brick = 1 kilogram and half a brick IS heavy." ... Again, you're reading it wrong, it clearly has no "IS" in the original between brick and heavy.

So just read the riddle verbatim:

1B = 1Kg + 1/2B

The word "and" does indicate an addition. Its like if I said, I have one apple and 3 oranges. Exactly like saying 1apple+3oranges.

So...
1B = 1Kg + 1/2B
1B - 1/2B = 1Kg
1/2B = 1Kg
B = 1Kg/(1/2)
B = 1Kg*2
B = 2Kg

Voil?
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### #24 tomb228

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Posted 07 November 2007 - 09:55 PM

Brick - Back to the Logic Puzzles
An old riddle is as follows: One brick is one kilogram and half a brick heavy. What is the weight of one brick (previously: How heavy is one brick)?
(This is a typical elementary math brain teaser.)

Since it was ambiguously phrased as "one brick is one kilogram" there is no way to know the answer definitively. Your algebra is correct but there is no way to tell if you interpreted the question right. Just be glad the homonymy of the English language gives us all pointless things to argue about. After all, we could be working
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### #25 jxcole

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Posted 09 November 2007 - 05:37 AM

This is the solution I originally thought up. It is an extremely extremely strange way to do it:

A brick is one kilogram plus a half a brick. So, we start with a brick is 1 kilo.

But if it is 1 kilo, clearly the weight of the brick must be 1.5 kilos, because the weight is 1 kilo plus half a brick.

Similarly, if the brick weighs 1.5 kilos, it must, by logic, weigh 1.75 kilos, since, after all, half of 1.5 is .75 and a brick is 1 kilo plus half a brick.

But then again, the brick does not weigh 1.75 kilos, it must clearly weigh 1.875 kilos by the same logic.

This series is clearly converging, but to what? If we write it out:
1 + 1/2(1 + 1/2(1 + 1/2(1 + 1/2(.....))))
or the other way
...(1 + 1/2(1 + 1/2(1 + 1/2)))
So we are left with the relation
a[0] = 1
a[i] = 1 + 1/2 * a[i-1]

Anyway, I don't want to do any more calculus, but it is clear this sum converges to 2. I just thought that was a fun way to do it.
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### #26 eleftheria

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Posted 16 November 2007 - 03:15 PM

x=brick weight
x=1+1/2x
1/2x=1
x=2kg
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### #27 SMARTCHIC

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Posted 15 December 2007 - 12:09 AM

that is sssssssssssssooooooooooooooooooooooooooooooooooooooooooo stupid even my mom said so. netwebdave explanied it to me thanks
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### #28 alien1

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Posted 17 December 2007 - 01:56 AM

A brick weighs 2 Kg + 1/2 a brick. Therefore, 1/2 brick + 1/2 brick = 2 Kg, so 1/2 a brick weighs 1 Kg.

Hence 3 half bricks must weigh 3 Kg.

Alien1
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### #29 alien1

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Posted 17 December 2007 - 02:03 AM

Sorry people,

I was thinking in pounds, which would have been 3.3 pounds .

The answer should be one and one half Kg.
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### #30 monstercojones

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Posted 31 January 2008 - 09:26 PM

This is my first visit to the site, and I've never posted before, but I found the discussion interesting and figured I'd throw my .02 in.

An old riddle is as follows: One brick is one kilogram and half a brick heavy. What is the weight of one brick (previously: How heavy is one brick)?
(This is a typical elementary math brain teaser.)

I think the intent of the riddle is weight = mass, so we can throw all the weight vs. mass debates out the window, it just complicates things.

If one follows the algebraic interpretation of this riddle, one would be inclined to assume that the equation would look like this:

1 brick = 1kg + .5 brick

or

1x = 1kg + .5x

so

1x - .5x = 1kg

.5x = 1 kg

x = 1kg/.5

x = 2kg

the 2 kg answer is correct, but the wording of the riddle is slightly flawed and open to interpretation. If we look at the problem as parsimoniously as possible, which is likely what the riddle-maker intended, it yields a logical answer of 1 brick = 2kg.
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