Omnimaga

General Discussion => Other Discussions => Math and Science => Topic started by: Happybobjr on November 27, 2012, 08:02:17 pm

Title: 8 Balls
Post by: Happybobjr on November 27, 2012, 08:02:17 pm

Ok, after seeing Builder's awesome riddle, which I solved (ok, not really), I figured I could be nice and make you think of two at once. >:D.


You have 8 identical Blue Lobsters and one balance. Lets say it looks like this.
(http://www.google.com/url?source=imglanding&ct=img&q=http://static-p1.photoxpress.com/jpg/00/11/79/69/400_F_11796960_59iASO32QmUM8iVuyIb8Fp1ZyjR3KQFG_PXP.jpg&sa=X&ei=qWC1UPKhKpStyAHH3IGIAw&ved=0CAkQ8wc4Pw&usg=AFQjCNHPZb3L8wEcl52TRCJtjzvX6wpYAw)

One of the lobster's weighs slightly more than the rest, but you can't tell by holding it or anything.  You are overcome with the sudden urge to know which one is the one that weighs more.  Warning though, you have only time enough to use the balance twice before Netham attacks you with a Banana Razor!  How can you tell which is the heavier?

Spoiler For In other words:

1) 8 lobsters. 7 weigh same. 1 weighs tiniest bit more.
2) 1 balance
3) You can only use the balance twice
4) Find the heavier lobster

Same rules apply to mine as his. There is no trickery.
You can't just say 'Oh! this one feels like it might weigh more.
Good luck.

Title: Re: 8 Balls
Post by: dinosteven on November 27, 2012, 09:40:22 pm

Spoiler For My Answer:

Weigh 3 lobsters against 3 lobsters.

a: If they're the same: Weigh the remaining 2 lobsters and the heavier lobster is the one you want to find.

b: If they're different: Take the 3 lobsters on the heavy side. Measure 1 lobster against another.
b1: If they're different: The heavier lobster is the correct one.
b2: If they're the same: The 3rd lobster not weighed is the correct one.

Title: Re: 8 Balls
Post by: Happybobjr on November 27, 2012, 10:19:20 pm

yup

Title: Re: 8 Balls
Post by: dinosteven on November 27, 2012, 11:06:41 pm

Yay! This is the 1st brainteaser I've been able to solve.

Title: Re: 8 Balls
Post by: Scipi on November 27, 2012, 11:12:22 pm

My answer:

Spoiler For Spoiler:

Divide into two groups of three and one of two

Weigh the two groups of three against eachother and of one is heavier, measure two out of the three. If one is heavier than the other, that' the one, else it's the third one you didn't weigh.

If both groups of three weigh the same, weigh the remaining two and whichever is heavier is it.

Probably the same as the correct answer :P I've seen questions like this before.