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Homework Help: 6th grader enigma

  1. Oct 9, 2006 #1
    This is supposed to be a 6th grade problem.

    using integers 8 4 2 1 in order, create an equation to equal 18 and another to equal 19. you may use + - % X and exponents (^) in the same order.

    Now if the integers and operands (including exponent) are to be in any order then the answers are simple.

    8 + (4+1)*2 = 18
    8*2 + 4 - 1 = 19

    But, if not only the integers 8,4,2,1 are to be in order, but also the operands, then it seems impossible.

    I think the integers must be in order at least. Can anyone see if it's possible or not to answer this question with integers in order but the operands in any order?

    Integers are to be used once only.
    Operands can be used multiple times.
  2. jcsd
  3. Oct 9, 2006 #2
    I don't see how the operands can even be used "in order." At most, only four will be used--and there are five given.

    Anyway, my guess is that the exponent operand may have been given as ^2 (i.e., squared). Then,
    (8-4)^2 + (2*1) = 18
    (8-4)^2 + (2+1) = 19
  4. Oct 9, 2006 #3
    I would guess that the order of operands is simply that the use of the operands should follow that order of preference. + - % X ^.

    Nice answers. It's just that the integers are only allowed to be used once only - AFAIK!
  5. Oct 9, 2006 #4
    If you need to use the operative in order than I must say it seems impossible.

    Can you use the factorial function?
    (8 - 4! - 2) * (-1) = 18
    (-8) + 4! + 2 + 1 = 19

    Oh...... and AFAIK?

    The Bob (2004 ©)
    Last edited: Oct 9, 2006
  6. Oct 9, 2006 #5
    Since I can't do this problem, then thanks for saying it seems inpossible as it is.

    Factorial function not included, I'm afraid :(, nice one though :)

    AFAIK == As Far As I Know.
    AFAIAA == As Far As I Am Aware.
  7. Oct 9, 2006 #6
    Oh ok, cool......... cheers. :biggrin:

    I do believe it is impossible, if the order of the numbers and the operations has to be the same as you stated. I think the best thing to do is to prove it cannot be done, rather than it can be done.

    The Bob (2004 ©)
  8. Oct 14, 2006 #7
    Maybe ...just maybe , u read the question wrongly.....

    Like what Knavish answered at first.....maybe the operands can be used only once ...n the interger in the order....

    interesting question......

    ntg is impossible!!
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