This is a question i received during a business interview for an internship. I couldn't get the answer.?

Question

The interviewer said: Imagine you have 8 balls that are exactly identical. 7 of the balls weigh the same. 1 ball weighs slightly less. The difference in weight is miniscule and therefore you cannot decide by holding them in your hands. You have a scale that measures weight. You can only use the scale, to calculate two measurements and two measurements only. How would you identify the ball that weighs slightly less??

Answer 1

this is simple.it may seem hard at first, but once you learn this.. you'll think the same way about it.

first you take any six balls and put three on each side of the scale...
if they are even you have eliminated all six of them..and you go on and weigh the other two

if they are not even, take two balls from the lighter side and weigh them... again.. if they are the same..they are eliminated, and the ball that was never weighed would be the lightest one,

but if they were not equal.. the lighter one would be your ball

hope this helps :)

Answer 2

Okay. You have balls 1,2,3,4,5,6,7,8

Weigh 1, 2, 3 against 4, 5, 6
If they are equal, then you can find the lighter one by weighing 7 against 8

If, say, 4, 5, 6 is lighter, then set aside all other balls. Measure two of those against each other. If it's equal, the one set aside is the culprit.

Answer 3

This is right assuming that you mean a digital reading scale - Put them all on the scale at once, and start removing them one by one, and you'll find that one removes from the weight showing a slightly higher amount than the one removed before it (or in the case of the first ball removed, the one removed after it). You will have to remove at least three to figure out which one is the unique one.

If you are using a BALANCE scale, then the answer is below

Answer 4

eeny meeny miney moe???

I guess you'd just have to weigh 2 of the balls and hope that one of them weigh's less than the other.

if the 2 balls you chose were exactly the same weight - at least you could eliminate those 2 and then there's a 1 in 6 chance of guessing randomly out of the rest.


???

That's a hard one.