Sorry calculated wrongly, should be 5 :)markop2003
Nope. It's 3.What you do is divide the 27 into 3 groups of 9. You place one group on one side of the balance and another group on the opposite end. If the balance moves one way, you take the group that weighed less. If the balance was level, you know that the group that was not used has the stone.
Now you take whichever group that had the stone and divide it into 3 groups of 3 and place 2 of the groups on balance like before. If the balance goes one way, you know which group on the balance has the stone, and if it stays you know the unused group has it. Now you have 3 choices.
For your third and final use of the balance, you place one stone on one side and another on the other. If the balance tilts, you have your stone on the elevated side, and if it stays balanced, the unused stone is the lighter stone.
Log in to comment