A really hard riddle

[pshreck]

There are ten bags containing marbles. Each bag has at least 10 marbles in it. Nine of the bags contain only marbles weighing 10 grams each. One of the bags contains only marbles weighing nine grams each. Each bag has a different number of marbles in it. All of the marbles look exactly the same.

How can you isolate the nine gram marble bag if you can only use a scale once?

EDIT: I just realized its much easier than I thought to get the answer to this on the web. Please try to do it honestly, and if you already knew it then stay silent /images/graemlins/cool.gif

[LALDAAS]

Put all the bags on the scale removing 1 bag at a time, then subtract the diffrance per bag.Then divide the number of marbles by the wieght per bag.

Thats only using the scale once.

???

My best guess.

[manpower]

I think i got it, I'll post my answer later.

[pshreck]

[ QUOTE ]
Put all the bags on the scale removing 1 bag at a time, then subtract the diffrance per bag.Then divide the number of marbles by the wieght per bag.

Thats only using the scale once.

???

My best guess.

[/ QUOTE ]

This is considered using the scale multiple times.

[bholdr]

THIS IS THE ANSWER- IF YOU WANT TO FIGURE IT OUT ON YOUR OWN, DO NOT READ:

i think this is a variant of many other riddles i've tried, this solution should work, but i think there are others...


weigh, all at once: 1 marble from bag one
2 from bag two,
and so on.

if all marbles weighed the same it should weigh 10+9+8+7 etc grams.

if it is off by 10 grams, it is the bag from which you pulled 10 marbles. if it is off by 4, the 4 marble bag, etc...

this was an easy one. gimme something HARD! (maybe i'll post one of my favs soon)

[Mano]

By scale, do you mean a balance, or does it actually give you the total weight in grams of what you are weighing (if that is the case it is a pretty easy problem).

[brassnuts]

bholdr has the correct answer.

[TimM]

Answer in white:

<font color="white">
Line up the bags and assign them numbers 1 through 10. Take 1 marble from bag 1, 2 marbles from bag 2, etc. Weigh this entire batch of 55 marbles. Subtract the result from 550. The answer is the bag number containing the 9 gram marbles.
</font>

[manpower]

Same as mine, except I would have counted the number of marbles in each bag, and since they are all different numbers, remove the offending bag that way.
[edit: grammer]

[bholdr]

now that i think about it some more, i realize that this was on a "columbo" episode, where a MENSA member is murdered, and the head of that mensa chapter, the suspect, challenges columbo with a simaler riddle, and he solves it, to prove that he's a smarty too.

[mmbt0ne]

</font><blockquote><font class="small">En réponse à:</font><hr />
this was an easy one. gimme something HARD! (maybe i'll post one of my favs soon)

[/ QUOTE ]

Let me find one of GoT fame. Aha.

</font><blockquote><font class="small">En réponse à:</font><hr />
This is a famous puzzle that I was never able to solve. I do possesss the very difficult solution... have fun GoT. You asked for a tough one, here you go.

Three gods A, B, and C are called, in some order, True, False, and Random. True always speaks truly, False always speaks falsely, but whether Random speaks truly or falsely is a completely random matter. Your task is to determine the identities of A, B, and C by asking three yes-no questions; each question must be put to exactly one god. The gods understand English, but will answer all questions in their own language, in which the words for “yes” and “no” are “da” and “ja,” in some order. You do not know which word means which.

-RMJ

[/ QUOTE ]