Saturday, 19 March 2011

One cream or two?

Answer to the last riddle: Separate the pile into two piles of 13 and 39, both with an unknown number of faceup cards. Now flip over the pile of 13. You now have the same number of faceup cards in both piles.

Didn't know what to make of that one eh? Hm. I had a hard time believing it too, had to try it out for myself. In fact, you can prove it algebraically (a cookie for whoever can show me this proof in the comments!)

Consider two identical cups, one half-full of tea, the other half-full of milk.  You take a teaspoon of milk from the milk cup and put it in the tea cup.  Then you take a spoonful out of the tea cup and put it in the milk cup. You take another spoonful out of the milk cup and into the tea cup, and one final spoonful from the tea cup to the milk cup. Now: is there more tea in the milk cup, or more milk in the tea cup? 

38 comments:

  1. There is more milk in the tea cup.
    Unless it is half tea/half milk in each cup, then i suppose it is even..

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  2. both remain the same? it doesn't say what spoon is full of when you place it back and forth.

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  3. Algebra for yesterdays:
    Face up cards in deck of 13 cards = x
    Face down cards in deck of 13 = 13 - x
    Face up cards left in main deck = 13 - x
    Therefore flipping over the deck of 13 makes the 2 decks have an equal amount of face up cards :)


    As for todays riddle. Both will remain the same no matter how many spoonfuls you swap over. As the volume of each cup will stay the same as it started then any milk missing from the milk cup will have been replaced by tea and the volume of tea needed for that will have been replaced by milk.

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  4. hmmn, still thinking it over. I'll get back to you when I've solved it

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  5. Am I really this dumb or does anyone else still find this confusing? xP

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  6. shit, i´m horrible in this thinks..
    lol..

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  7. I'm going with milk on this one.

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  8. I wanna say they both remain the same.

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  9. it's more chaotic that's for sure

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  10. love your blog
    following and $upporting

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  11. There should be more milk in the tea cup. I think...

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  12. great background on this, bro!

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  13. Both the same assuming the volumes in both cups are equal

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  14. I want to say more tea in milk cup.

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  15. This blog is awesome! I love riddles! I'm gonna say there's a mixture in each of them since you kept mixing both of them.

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  16. this blog is amazingly interesting! i can't do the things right now but as soon as i get home i will!

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  17. There's more milk in the tea cup

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  18. They are the same.. I think.

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  19. More milk i tea cup i suppose.
    Im not sure though.
    Btw awesome blog! I love brain teasers, followed! ^^

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  20. loving the riddles man, keep it up

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  21. You say half full, but what's the OTHER HALF filled with?! EH EH?!

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  22. the answer is the tea and milk is on the floor cause i spilled it

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  23. I believe both would be equal.

    Supported.
    bigunicorn.blogspot.com

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  24. I'm not really sure. I would assume it would reach equilibrium at a certain point.

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  25. Where do you get this! They are tuff

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  26. There's more milk in the tea cup, as the first spoonful was undiluted, and each spoonful thereafter was progressively more dilute.

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  27. The mixing ratios are equal. Calculated it. :D

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  28. i thought they would;both remain the same

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