Last Question:
You have sealed the ninth of nine identical parcels of precisely equal weights, only to discover that your diamond ring has accidentally fallen into one of the packages.
You don’t want to unwrap every parcel. Can you work out how to find the parcel containing the ring with just two weightings of the parcels?
Answer:
Weight three parcels against three parcels. If one side is heavier than the other side, one of the three parcels on the heavier side must contain the ring. If both sides are equal in weight, the ring has to be in one of the three parcels that were not weighed.
From the group of three that you now know contains the ring, weigh one against the other. The heavier of the two now has the ring; if both are equal, the ring will be found in the unweighted parcel.
Today’s Problem:
A sealed bottle containing 48 flies is placed on a weight scale.
When does the scale register the heaviest weight:
When the flies are resting on the bottle of the bottle or when all 48 flies are in flight?