You have been given 9 weights, one of which is slightly heavier than the rest.

Can you work out which weight is heavier in just two weighings of the balance?

Can you always work out which weight is heavier in just two weighings of the balance?

Could you always work out which is heavier in just two weighings if you had been given 10 weights?

You have now been given 27 weights, one of which is slightly heavier than the rest. Can you work out which weight is heavier in just three weighings of the balance?

Can you always work out which weight is heavier in just three weighings of the balance?

You now have 9 weights again, and know that one is a slightly different weight, but you don't know if it is heavier or lighter.

Can you work out which weight is different, and whether it is heavier or lighter, in just three weighings ?

Can you explain how you would always be able to tell in just three weighings ?

Could you always work out which is the odd one out in just three weighings if you had been given 10 weights?