How can I identify an alloy from gold?

Question

I have 8 balls of which 7 are pure gold and one is an alloy. It is not possible to identify by seeing. I have given to use beam balance but twice only. Can you tell me how can I identify the alloy by using the beam balance two times?

Answer 1

U can find out the alloy ball by using the beam balance twice ONLY if u know the alloy ball is lighter or heavier than the gold ball.

If you don't know whether the alloy ball is lighter or heavier, then u need 3 weighings with the balance and the problem gets complicated !

Answer 2

weigh  3  ==  3

if one set is lighter weigh  1  ==  1  if they're= then it's the 3rd

if the first is =

then weigh the remaining 2, and the lighter is the alloy