you have 8 iron balls all balls look the same feel the same
but 1 ball is counterfeit, you can't notice the difference except by using a balance on your side, you can only use the balance twice
figure it out, have fun
You've more or less given us the answer in the question.
The usual question is "You have 8 balls. 7 of equal weight, and 1 that is slightly heavier. You also have a pair of scales. What is the minimum number of times you need to use the scales to work out which ball is counterfeit?"
But it works either way.
And yes, I know the answer, but I'll wait for others first. In fact, I'll answer it when I wake up in the morning - even if no-one has answered they'll have had enough time to... and I won't wake up until gone midday.
Split the balls into 3 piles - two of 3 and one of 2.
Take the two piles of 3 and weigh them against each other. If one side goes down, then take two of those three balls and weigh them against each other - whichever side goes down is the counterfeit ball. Should neither go down then the third ball (the one you haven't weighed) is the counterfeit ball.
Should neither side go down when you put the piles of three on then the pile of two countains the counterfeit ball, in which case you just weigh the two against each other and whichever goes down is the heaviest and therefore the counterfeit ball.
8 balls 1 scale
Linear Mode
