Question

you have nine identical balls and among them one is defective as it weighs more than the rest .you are provide with a physical balance .what will be the minimum number of times you should use the physical balance to figure out the defective ball?

Answer 1

make three sets of three balls each A,B,C

now keep set A on one side of weighing balance and set B on another side.(weighing 1)

CASE-1 if one of the side is heavier than the other, you have found the defective set

CASE-2  if both the sets are equal then set C contains the defective ball,

so now we are left with the defective set having 3 balls.

now keep one ball at one side of weighing balance and other ball on the other side of weighing balance.(weighing 2)

CASE-1 if one of the ball is heavier you have found the defective ball.

CASE-2 if both the balls are equal then the third ball is defective

so minimum two weighings ae required to figure out the defective ball

i hope it helps

thank you for such an interesting question:)