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| So you think you're clever 2? |
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| Learner |
| 05/11/04 at 14:14:17 |
| [slm] The challenge has been set 8) ...startinng from....NOW! 1. How is it possible for there to be a perfectly straight line such that its ends are higher than its middle? 2. How can you throw a ball so that it goes a short distance, comes to a total stop, reverses its motion, and then goes the opposite way. You are not allowed to bounce it against anything, hit it with anything, or tie it to anything. 3. You have a pile of 24 coins. Twenty-three of these coins have the same weight, and one is heavier. Your task is to determine which coin is heavier and do so in the minimum number of weighings. You are given a beam balance (scale), which will compare the weight of any two sets of coins out of the total set of 24 coins. How many weighings are required to identify the heavier coin? |
| Re: So you think you're clever 2? |
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| Mossy |
| 05/11/04 at 16:17:36 |
| Salam, 1. Draw it on the ball you throw up in part 2 2. Throw it straight up 3. 5. Divide the coins into two groups of twelve. Put each on either side of the scale. Eliminate the lighter group and split the next group into two groups of six, placing one on each side and doing likewise. Do this for two sets of three coins. Do it once more. You are down to three coins having had 4 tests. Now put two of the three coins on the scale. If the scale balances, it is the remaining coin. If the scale does not balance, it is the heavier coin on the scale. |
| Re: So you think you're clever 2? |
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| Aadhil |
| 05/11/04 at 21:58:24 |
| [slm] 1. Man easy for a mechanical engineering major. Take a piece of string, hold it on both ends. let the middle sag, and look at it from the top. Ends are still higher but looking from the top you see a straight line. 2. Ditto as Mossie. 3. Dont have a clue (I hate math :P). |
| Re: So you think you're clever 2? |
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| ft |
| 05/13/04 at 18:59:30 |
| 3. 3 Trials. Here is how. Divide the coins in 3 groups of 8. lets say piles a,b and c, weight a and b, if both are the same weight, c is the one with the heavier coin, otherwise a or b would be the heavier set. Lets say c is the heavier one, divide that into groups of 3, 3 and 2. weight the groups of 3, if they are the same, the heavier coin in the pile of 2, otherwise it will be in one of the piles of 3. If it's one of the 2, weigh them and you get your heavier coin. If its in one of 3. Weight two of them with each other and the result should tell you which one of the three is the heaviest. |
| Re: So you think you're clever 2? |
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| Mossy |
| 05/13/04 at 21:32:48 |
| Ahh, cunning :D I can't count, my way was actually four ??? And I'm meant to be a maths major.. :'( |
| Re: So you think you're clever 2? |
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| CAMuslimGirl |
| 05/15/04 at 00:48:01 |
| [slm] :-) #3: It would take no weighings at all. One of them is a different coin than the others (ie one is quarter, others are all pennies). ;) |
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