Brainteaser  20190612  DE Shaw

Given 9 balls all of which weigh the same except for one, what is the minimum of weighings necessary to find the ball that weighs more (or less)?

@rishi 1 is the answer. Just throw all the balls in water and the one that is heavy or light will go down or stay up than the other balls.

@VamsiVishwanadh  Really good attempt, but what if the difference is really small? What if all the balls stay up or go down?

Place any random 4 on each side ...if the least one is in some side that will lean that side or else 9th one will be the one ...from that four place 2 each on balance and ..in the same way another time...so no of times we use balance would be 3

@PruthviRaj Think harder, you are close!

If it is weighing machine then divide the 9 into 3 groups and weigh each of them . The group with least weight will weigh less then go for weighing the least group and you can get the odd one out.
(1,2,3) (4,5,6)(7,8,9)
Measure group 1 with 2 and 2 with three and three with one until you get unequal at the both ends .
Now take the least weight thing and measure individually again
It may take 2 attempts at the least .

@SaiSuhas Well done  right answer

@rishi answer is two


@rishi Two
