There are ten bags containing marbles. Each bag has at least 10 marbles in it. Nine of the bags contains only marbles weighting 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. The riddle is how can you know which bag has the nine gram marbles if the only device allowed to be used is a weighing scales which you can use only once?
2006-06-10 23:06:17 · 17 answers · asked by webby 2 in Education & Reference ➔ Trivia
It can be done in just one weighing and Brainandy has the right method BUT
(a) he means 550 grams not 55,
(b) you can do it with 1 marble from bag 1, 2 from bag 2 ... up to 9 from bag 9 ie 45 marbles in all, and compare the weight to 450 grams,
If it is lighter by n grams, then it is bag n you want,
If it is exactly 450 grams, then it must be bag 10 that you omitted from the weighing that you want,
However this mixes up the marbles, so a refinement is to leave them all in their bags, Mark the bags with the number of marbles each contains, say these range from 10-19 and the total number of marbles is therefore 145 and compare the weight to 1450 grams, it will be 10-19 gms lighter and the bag with that no of marbles is the one you seek,
NB we assume the weight of ten empty bags is known and can be factored into the calculation eg weights and ten further empty bags on one pan and ten full bags on the other pan,
2006-06-12 09:46:35 · answer #1 · answered by Anonymous · 8⤊ 0⤋
The riddle is very easy.
Each bag should have at least 10 marbles. Each bag has different number of marbles.
Let's say bag A has 10 marbles
B has 11
C has 12
D has 13...so on...
J has 19 marlbles.
Now, you pick up a bag randomly and weigh. If the weight is in the multiple of 9 or if the weight is 90 grams, it is the one with 9 grams marble. Here's the explanation :
If A has 9 grams marbles, its weight would be 90, if it is 10 grams marbles its weight would be 100 grams.
If B has 9 grams marbles, its weight would be 99, if it is 10grams marbles its weight would be 110 grams.
So on.
What you need to rectify here is that you will have to allow to weigh at least 9 bags.
2006-06-11 00:27:39 · answer #2 · answered by pranesh81 3 · 0⤊ 0⤋
Put one marble from the first bag, two from the second, three from the third and so on. In theory, this should add up to 55 grams but in practice it will weigh a certain amount less. If, for example it weighed 3 grams less, then the dodgy pile is the third bag of marbles. If on the other hand it weighed 7grams less then it would have come from the seventh bag etc.
2006-06-11 05:35:05 · answer #3 · answered by brainyandy 6 · 0⤊ 0⤋
My guess is that you have to take the marbles out of the bags first. Assuming that there is no mix of 9g/10g marbles within any of the bags, if you weight a marble from each one individually, and the scales are accurate, you'll find out in no time.
2006-06-10 23:13:58 · answer #4 · answered by Buzzard 7 · 0⤊ 0⤋
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2016-12-08 19:25:58 · answer #5 · answered by ? 4 · 0⤊ 0⤋
all the 10 gram marbles would be multiples of 10 IE. 10,20,30 etc.
all the nine grams would be multiples of 9 . ie.9,18,27etc.
the only common weight would be 90 grams
10x9 or 9x10. In this case i presume it would be allowed to count the marbles.
2006-06-12 10:03:48 · answer #6 · answered by M.T.brainbox. 1 · 0⤊ 0⤋
Put all the bags on it at once and then just continue with that until you have a mishap with the #'s.
2006-06-10 23:22:33 · answer #7 · answered by Anonymous · 0⤊ 0⤋
put all the bags on the scales and remove them one at a time and check to see when the weight goes down by nine grams
2006-06-11 11:11:29 · answer #8 · answered by species8472 6 · 0⤊ 0⤋
You just made my brain hurt. Who really has the time to sit and solve these god forsaken riddles unless you have nothing else to do.
2006-06-11 13:31:40 · answer #9 · answered by ? 2 · 0⤊ 0⤋
seriously....its better to play with marbles than worry about their weight or which bag holds them.
2006-06-11 02:49:47 · answer #10 · answered by Anonymous · 0⤊ 0⤋