Question

You have 9 stones that are identical in appearance. One of these stones weighs just a bit more than the other 8. These other 8 stones are exactly the same in weight. Using a balance scale only TWICE, how can you determine exactly which stone is the heavier?

Answer 1

i think you can weigh it 3 and 3.
If they balance, choose set not used.

If not balanced, take the heavier side

then weigh 1 and 1
if balanced, stone not used, if not balanced, take the heavier side

hope this helps