Tuesday, September 23, 2008

OK so this is the first set problem for IMO 2009 students as well as for all young mathematicain. lolz.

1)Suppose there are seven coins, all with the same weight, and a counterfeit coin (fraud coin) that weights less than the others. How many weighings are necessary using a balance scale to determine which of the eight coins is the counter feit one? Give an algorithm for finding this counter feit coin.


Hint: the ans is only 2. lol

2) solve the same problem in case there are 11 coins and 1 counterfeit coin which is havier than others. (if possible try to solve the problem in case n coing and 1 lighter counterfeit coin)

OK here is the last one:

3) Each inhabitant of a remote village always tells the truth or always lies. A villager will only give a "yes" and "no" response to a question a tourist asks. Suppose you are a tourist visiting this area and come to a fork in the road. One branch leads to the ruins you wan to visit; the other branch leads deep into the jungle. A villager is standing at the fork in the  road. What the only ONE question you can ask the villager to determind which branch to take?

Hint: use logic lol, 

OH by the way smey, I have invented some java program that do some benefit job for math such as 
1 ) test whether a 9*9 table of an interger is a soduku or not. 
2) factorial a positive numbe for example : 60= [2^2].[3^1].[5^1]
dunno what else. lol just hope i can post on this website to reduce the time for calculation of math students. when i was in highschool if i want to factorial big number or test whether a number is prime or not it take so long. but now it take less than 1second lol.



Regard,
Old generation

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