2 Times. First 3vs3, from here You know wich group of 3 balls contain the havier one. You take the group with the havier one and then you balance 1v1 and you know wich is the heavier
#BrainTeaserTuesday: You have nine balls, but one is heavier. How many times do you need to use a balance scale to find the heavier ball? 
(Solution here: http://khan.co/9BallsTW )
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Before checking, I think 3 times. First time measure 4 vs 4, and if they don’t balance, do 2 vs 2 with the heavy 4, then 1v1 with the heavy pair and that’s your ball. If the first set balanced, then the one you set aside is the heaviest.
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I watched the video and it was not as I expected!
End of conversation
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2 times. Divide them in groups of three. Compare two groups, you will know which group has the heavier ball. Now take two balls to weigh from the respective group, you will get the heavier ball.
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maximum three times i need to use scale
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Floor(Log base 3 (n)) in the general case?
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very interesting video , answer is two, god bless
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What if I choose the heaviest ball and one normal weight ball by luck at the first attempt? So it depends on luck! Bytheway the 4 th ball from left is the heaviest one. I always trust my luck
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