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Can you solve this brainteaser?

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re: Can you solve this brainteaser?
2/28/2008 8:20:14 AM
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Max- I think that this is a trick question. You simply pick up the end of the string and the answer is 1 meter.

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re: Can you solve this brainteaser?
2/28/2008 8:27:40 AM
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I think Buck has got it right. Diameter increases by 2m. C=pi*(D2-D1)= pi*2 = 6.28m gap in string.

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re: Can you solve this brainteaser?
2/28/2008 9:48:35 AM
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L = 2 * Pi * R dL/dR = 2 * Pi Therefore, increasing the radius with 1m gives 6,28 m extra length, no matter the original radius (or length). /Peter

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re: Can you solve this brainteaser?
2/28/2008 11:07:10 AM
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NO extra string needed to fill the gap if we could move our position towards southpole or northpole a little.

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re: Can you solve this brainteaser?
2/28/2008 12:32:12 PM
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It would be interresting how this equation looks, which gives the result how far we have to move to north or south... A real topic for my math teacher, who teased me with such questions back in school some decades ago.

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re: Can you solve this brainteaser?
2/28/2008 2:41:52 PM
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If we assume a perfect circle of string then we can calculate the Diameter D C=Pi x D D=C/Pi = 40x10^6/Pi When you lift the string by 1 Meter, the diameter increases by 2 Meters. Then all you need to do is calculate the new circumference C and take the difference between old and new. NewC=(C/Pi + 2) x Pi To get the difference: Difference = NewC ? C = [(C/Pi + 2) x Pi ] ? C. = C + 2xPi ? C = 2xPi The answer I get is 2xPi Rick.

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re: Can you solve this brainteaser?
2/28/2008 5:06:25 PM
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If string is lifted 1m, effective diameter increases by 2m. let d = 2meters. If D is original diameter then difference in circumference is C = (Pi*(D+d) - Pi*D) = Pi*d = 2*Pi meters = 6.283 meters

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re: Can you solve this brainteaser?
2/28/2008 5:27:47 PM
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I don't think any extra string is required. You already have 40,000 kilometers worth, which is way more than enough to encircle the earth.

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re: Can you solve this brainteaser?
2/28/2008 6:59:28 PM
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Correction, I confused diameter with circumference. The diameter comes out to just over 40,000 km.

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re: Can you solve this brainteaser?
2/28/2008 7:00:01 PM
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on a completly different tangent: the string would stretch the extra approx. 2m as the requirement didn't specify tension to remain the same.

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