Monday, November 16, 2009

TV

Watched the telly last night for a bit. Whoever said that the adverts are the best bit was clearly barking. I really am sick to death of Christmas; thank God its nearly over.

If moving sedately from side to side whilst waving some sort of game controller at the tv is our main weapon against the rise in obesity, then we really are stuffed.

Here's a puzzle someone told me over the weekend:

There are eight identical looking balls on the table in front of you along with a set of balance scales. (One of the balls is actually a bit heavier than all othe others) You don't get to touch any of them, you just tell me which balls to put on the scales. I will do two weighings and then you must tell me which is the heavier ball. (Each side of the balance scales is big enough to fit as many balls on it as you like)

8 comments:

Anonymous said...

I haven't googled this, honest.

First, put three balls in each pan. If one side is heavier, it must contain the heavy ball; if not the heavy ball is one of the two that aren't on the scales. If it's the second case, simply weigh the two balls and pick the heavier one. In the first case, weigh any two of the three balls from the heavier pan. If they are different, pick the heavier one, if not the heavy one must be the third ball from that set.

Anonymous said...

There is another version where you have 12 balls, can use the scales 3 times but do not know whether the odd ball is heavier or lighter.
Jobrag

Roue le Jour said...
This comment has been removed by the author.
Mr Natural said...

A variant of this puzzle is as follows.

You have 12 coins; all appear identical, but one is slightly heavier or lighter than the others. How to you find the odd coin and determine whether it is heavier or lighter using the balance only three times?

Lilyofthefield said...

Did the deleted comment have anything to do with weighing yer balls, I wonder?

Pity the poor M&S staff, Mr Chalk. I was in there yesterday and they had their ghastly advert on a continuous loop.

Mr Natural said...

I think my short-term memory must be on the blink: I hadn’t registered Anonymous’s second comment. ……………….

I think my short-term memory must be on the blink: I hadn’t registered Anonymous’s second comment. ……………….

I think my short-term ……… You’re not my daughter ….

Anonymous said...

MrN: Not sure you can distinguish between 12 results using 3 tests each of which gives 2 possibilities since 2^3 < 12 (if direction of scale's movement doesn't give useful info in this case, then it only measures equal or non-equal)

Anonymous said...

MrN: Not sure you can distinguish between 12 results using 3 tests each of which gives 2 possibilities since 2^3 < 12 (if direction of scale's movement doesn't give useful info in this case, then it only measures equal or non-equal)

Yes it is possible
Jobrag