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If 7x7=4 11x7=6 13x11=6

  1. Oct 11, 2003 #1
    If

    7x7=4
    11x7=6
    13x11=6

    Then

    27x28=?
     
  2. jcsd
  3. Oct 11, 2003 #2

    marcus

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    I'm impressed, Zaleski. Explain
     
  4. Oct 11, 2003 #3

    marcus

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    oops your answer changed from 8 to 6!

    I still believe you are right, and understand the problem,
    so please explain
     
  5. Oct 11, 2003 #4
    Originally, I posted 8. Here's how I arrived at that number.

    The difference between prime number 23 and prime number 19 is 4.
    The difference between prime number 29 and 23 is 6. Adding 6+4 you get 10. The number your looking for is 27, which is 2 less than 10 or the number 8. I think the number 6 may be another way of looking at it, i.e., 27-23=4, 29-27=2, 4+2=6.
     
  6. Oct 11, 2003 #5

    marcus

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    Thanks RZ, I dont understand you but I'm still impressed:smile:

    this problem has a nice open-ended character----maybe we
    will be getting further attempts!
     
  7. Oct 11, 2003 #6
    6

    it's the amount of 'e's in the number

    seven (2 'e's) x seven (2 'e's) = 4
    eleven (3 'e's) x seven (2 'e's) = 6
    thirteen (2 'e's) x eleven (3 'e's) = 6

    twenty-seven (3 'e's) x twenty-eight (2 'e's) = 6
     
  8. Oct 11, 2003 #7
    7x7=4

    11x7=6

    13x11=6

    17x13=6

    19x17=6

    23x19=10

    29x23=8

    31x29=



    Your subtracting the second number in a top row by the first number in the row below it, i.e., 11-7=4, 13-7=6, 17-11=6, etc.

    Therefore, 27x28=8 (27-19=8)
     
  9. Oct 11, 2003 #8
    I just noticed, this isn't a brain teaser, it's a Brian teaser.
    Too bad I don't know anyone called Brian. =P
     
  10. Oct 11, 2003 #9
    RZ -- i thought of that too, but what you did assumes that each "equation" canNOT be done independently, which doesn't seem right. you should be able to do these equations by themselves.

    in other words, the answer you get depends on the previous equations you have used.

    look:
    7x7=4

    11x7=6

    13x11=6

    17x13=6

    19x17=6

    23x19=10

    [27x28 should come right here, but it gets "skipped over" according to your rules (27x28 does not exist in your scheme)]

    29x23=8


    i think Asimir gets the point
     
  11. Oct 11, 2003 #10
    Well, we gave it a try Brum. Asimir answer looks like a winner.
     
  12. Oct 12, 2003 #11
    Perhaps each number in the left side of the equation represents an alternate number


    7x7=4 this is really: 2 x 2 = 4 so 7 = 2

    11x7=6 if 7 = 2 then 6/2 = 3 so 11 = 3

    13x11=6 if 11 = 3 then 6/3 = 2 so 13 = 2



    Then

    27 x 28 = 48


    27 ---> 7 + 7 + 13 which is really 2 + 2 + 2 or 6
    28 ---> 7 + 7 + 7 + 7 which is really 2 + 2 + 2 + 2 or 8


    And 6 x 8 = 48

    So then with the substituted numbers 27 x 28 = 48


    Hope I didn't make that too complicated!
     
  13. Oct 12, 2003 #12
    I'm impressed reddhawk, how come I didn't come to that idea. I don't think I'd need to post anything now.
     
  14. Oct 12, 2003 #13

    FZ+

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    Maybe x isn't an operator at all, but a variable representing that particular digit.

    ie.

    7x7 -> 747
    11x7 -> 1167
    13x11 -> 13611

    Then

    27x28 -> 27?28

    So we can consider these not as equations, but as a sequence of numbers.

    Sum digits:

    747 -> 18
    1167 -> 15
    13611 -> 12
    so 27?28 -> 9

    so 27x28 = -10
     
  15. Oct 12, 2003 #14
    Hint #1: Think about how the numbers are spelled.
     
  16. Oct 12, 2003 #15
    Each of the numbered words begins with one of three letters, i.e. ,S, E, or T.
    I’ve assigned each letter a number as follows:
    S=2
    E=3
    T=2

    Twenty Seven x Twenty Eight
    .......(2x2)......x........(2x3)= 24
     
  17. Oct 12, 2003 #16

    dduardo

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    Wow, im surpised no one has got this one. I thought there were a bunch of good answers. Well here my try from left field:

    7x7

    seven -> sev-en = 2 syllables

    so 2 x 2 = 4

    e-lev-en = 3 syllables

    so 3x2 = 6

    thirt-teen = 2 syllables

    so 2 x 3 = 6

    Finally 27x28

    twen-ty sev-en = 4 syllables
    twen-ty eight = 3 syllables

    4 x 3 = 12

    12 is my final answer
     
  18. Oct 12, 2003 #17
    dduardo gets the point! Good work everyone else though!
     
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