28 Aug 2022 11:29 am
Assume step 1 is even. that means one of your 4 yellow marbles is different.Cannonpointer » 28 Aug 2022, 11:21 am » wrote: ↑ If it is odd, then side a is either lighter or heavier. THERE ARE ONLY TWO SUSPECT MARBLES ON SIDE A.
Weigh them against each other. If side a was lighter, and they are even, then the side b suspect marble is the culprit - and heavier. If they are odd, then the lighter one is the culprit.
If side a was heavier, the elimination works the same.
If you put yellow marbles on both sides, 2 on the left, 1 on the right, and move the blue marbles accordingly so that there's 4 per side... If you get an unbalanced result, you know it's one of the 3 yellow marbles. But you don't know if it's heavier or lighter yet. You just know one of the three is the culprit. The yellow one on the right may be heavier, or one of the 2 yellows on the left may be lighter. We can't tell. And now you only have one chance left.
That's why you can't put yellow marbles on both sides, because it won't resolve the weight issue.