Question

You have 80 pearls. One is lighter than the remaining. What is the minimum number of weighings required on a common balance to ensure that the odd pearl is identified?​

Answer 1

Answer:

4 weighings.

Step-by-step explanation:

Divide the PEARLS in three parts of 27, 27, 26 PEARLS. Put both the 27 PEARLS parts on the balance pan. If both are equal in weight, then the third one has the lighter pearl, else the lighter of two has it.

Then divide them as 9, 9, 9 or 9, 9, 8. Follow the same procedure.

Then 3, 3, 3 or 3, 3, 2

Then 1, 1, 1 or 1, 1

So, after 4 weighings we have the lighter pearl