QUIZ Test #17- can you solve this? difficulty level: HARD

in mathematics •  2 years ago 

You have 12 balls, equally big and equally heavy - except for one, which could be either light or heavy.

You have only 3 chances to weigh the balls in any combination using the scales.
Find which ball is the odd one and if it's heavier or lighter than the rest.

How do you do it?

credit to @tensorflow for this interesting quiz

Quiz 11 still not solved:

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start with 3-3
if even, eliminate those 6, if uneven eliminate the 6 not used
move to 2-2
if even, eliminate those 4, if uneven eliminate the 2 not used
that's as far as I got, lol

nice try, maybe you can solve it. i will wait with the answer. maybe some1 will solve it, let's see. not that easy though

Okay, going to just go for this. Start with 6 and 6. Weigh.

Out of the lighter 6, split those into 3 and 3, weigh.

Out of the lighter of those, um, give up lol, this is hard, I'm going to chew on this for a while.

They're all the same volume, but one has a different mass (and they're all heavier than air)? Then you just need to measure density. Roll them down a slanted board. The one that reaches the bottom of the board at a different time is heavier/lighter. This experiment is not possible in a vacuum. Are we on the moon? I had 3 chances to weigh the balls and I needed 0. Do I get bonus points?

I got it! And in only two measures =)

  • Split the balls into three groups of four
  • Measure groups 1 and 2
  • Then measure the heavier group of above(lets call it group 1) and group 3.
  • If group 1 balances with group 3, then group two has a lighter weight ball.
  • If group 1 is heavier then group 3, then group 1 has a heavier weight ball.

how'd I do???