Vietnam Math Puzzle (How to make DoubleCakes Cry)

Discussion in 'Miscellaneous' started by LBoss9001, May 23, 2015.

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    I think a lot of people know the drill, For those who don't, Answer the Snake using the numbers 1-9 only once.
    This made me regret everything I never did in 3rd grade, b/c this is 3rd grade math
    ShelLuser likes this.
  2. Not sure I follow the logic here. You say that you need to fill in the numbers 1 to 9. But x - 10 = 66 automatically makes x (the last field) equal to 76.
  3. So fill in the rest of the fields to make 76 then...
  4. According to DC you can only use the numbers 1 to 9

    Edit: only once. Meh, that should be easy enough :p
  5. Ya, Use the numbers 1-9 only once
    Btw i didn't mention, a 8 year old made this.
    ...
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  6. So I looked this up on the Internet. And this is also how these puzzles get changed over time. According to DC you should use the numbers 1 - 9 only once. Making it possible to assume that you can also use other things. The page I referred to mentions that you can only fill out the numbers 1 to 9.

    In which case I still fall back to my previous issue of not following the logic here because the obvious value for the last entry is 76.

    Edit: Unless the logical importance of the math operands also applies here. For example: division comes before subtraction. However, that's not clearly mentioned and the snake approach makes it liable that you should proceed in the order dictated by the snake.

    Just like that other math puzzle I get the impression that some people make things up and others simply fail to correctly translate the actual question(s). Its very hard to correctly translate Eastern languages, especially because in many cases context is a big issue.
  7. I mentioned this to someone else too, Don't use Order of Operations here, Its very straight foward, So you add X+13 (so on so forth blah blah blah).
    My mum and I did Order of Operations and it didn't work, We guessed and checked.
  8. It wasn't an 8 year old that made it, this was in a test for 8 year old kids.
    So much yes.
    When you look at the picture, the first thing you assume is that you need to follow the order that is in the snake (a + 13, then result x b etc), but looking it up, it seems like you must first order it as an equation (https://www.youtube.com/watch?v=WiB2_dXSSMg).

    A lot harder to understand what the problem actually wants than to actually solve it.
    ShelLuser likes this.
  9. At last, Since 7AM my time, I have conquered this thing, If you want to know the answer, Pm me. :)
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    This is a math problem from Singapore. Why do us Americans not have math problems that actually get us thinking. It took me 30 MINUTES with no help before I found out the answer to this... I consider myself a good math student so... :rolleyes:

    You guys should solve this one too.
  11. I saw that one too, I want to solve it right now, but my brain looks like this right now
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  12. This problem involved logic more than math
  13. That is the puzzle I was referring to in my previous comment. Math isn't really an issue here since this is more about abstract mathematics. Funny too because a lot of people claim to know the answer but in doing so don't follow up on all the rules.

    Main rule: the information between the 2 lead players changes over time. And that time is also used to solve this puzzle of deduction.

    So, what do we know from the start: Albert knows the month of Cheryl's birthday whereas Bernard knows the day.

    Albert: I don't know when Cheryl's birthday is (note: impossible if you only know the month), but I know that Bernard doesn't know too.

    Bernard: At first I don't know when Cheryl's birthday is, but I know now.

    At this point we can eliminate May 19th and June 18th. Bernard can do his own deduction as well. But because he doesn't know the date it can't be any of these two unique days. Otherwise he would have known.

    So these are the days we have left at this point: May 15, May 16; June 17; July 14, July 16; August 14, August 15, August 17.

    Next we can eliminate June 17th because it's the only date which Albert could have deduced himself by month (which he didn't). Bernard now claims that he knows the date through deduction while only knowing the number.

    Because of the disappearance of June 17th there's only one single day number left which he could have come up with: August 17th. It's the only single number in the sequence at this time. After all: before the deduction of June 17th it could have been either June or August.

    Because Bernard says that he now knows Albert can confirm the same deduction. But the last line is basically meaningless.


    And yes, I know my answer is different from the "official" answer :)
  14. So this time with a much clearer mind I've actually concluded that my previous comment is wrong. And now I also see why ;) So one more time...

    Albert knows the month, Bernard the day.

    Albert: I don't know the birthday, but I know that Bernard doesn't know either.

    So at this point we know that May and June can be removed from the problem. Because these two months contain a single day: 19th only happens in May and 18th only happens in June. All Albert knows is the month, but for him to be sure that Bernard cannot know the birthday the date cannot be a month with a single non-overlapping day number in it.

    At this point we're left with: July 14 & 16, August 14 & 15 & 17.

    Bernard: At first I didn't know but now I know the birthday.

    First: the deduction which we did (eliminating May & June) is also something which Bernard did. When Albert said that he was sure to know that Bernard couldn't know the date he also gave Bernard a hint to do the same kind of deduction which we did. So Bernard can also deduce things to July & August.

    Next Bernard tells us that he knows the birthday. Therefor we can now deduce that it cannot be the 14th of July nor the 14th of August. Of course, at this point we don't know the date yet. Only Bernard does.

    All we know for sure is that the date is either: 16th of July, 15th of August or 17th of August.

    Albert: Then I also know when the date is.

    Albert only knows the month. But just like Bernard and us he followed the same rules of deduction. And he also knows that Bernard has done the same with thanks to his previous comment.

    So for Albert to know the date at this point it can only be a month without overlapping days. Which leaves us with the 16th of July.

    I guess this is why you don't drink certain beverages during exams ;)
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