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Is there a way you can get the number 5 from the numbers 6, 7, 8, and 9 using only addition, subtraction, multiplacation, and division, without combining two numbers e.g. using the 6 and 7 to create 67. Exponents, factorials, and trig functions are not allowed. If there is no way to do this, is there a way to prove that it is impossible? Thanks if you answer.

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  • $\begingroup$ Clearly nonunique. $\endgroup$ – Oscar Lanzi Jul 2 at 13:43
5
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$$\frac{8\times9}{6}-7$$

That seems about right!

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4
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$===================(7+8)/(9-6)$.

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4
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The code in my answer to your other question gives one more solution (after curating the output by hand)

7*(8-6)-9=5 (Bruno's solution)
(7+8)/(9-6)=5.0 (Oscar's solution)
8-6/(9-7)=5.0
8/6*9-7=5.0 (Zach's solution)
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  • $\begingroup$ (PS because the code performs an exhaustive search, this is all the solutions) $\endgroup$ – Calvin Khor Jul 4 at 0:32
  • $\begingroup$ Did you write the cases manually, or did you iterate over a list of functions? In second case, could I see the code? $\endgroup$ – Sudix Jul 5 at 1:13
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    $\begingroup$ @Sudix You may indeed see the code, its in the linked answer (you just need to change the 6 to a 5 (also I think you don't lose any solutions to floating point errors)) $\endgroup$ – Calvin Khor Jul 5 at 1:43
  • $\begingroup$ @Sudix (and remove the break points) $\endgroup$ – Calvin Khor Jul 5 at 1:53
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here is one other way to do it:

$$ (8-6)\cdot 7 - 9 = 5 $$

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  • $\begingroup$ @TheCount $(8-6)\cdot 7 - 9 = 2\cdot 7 - 9 = 14 - 9 = 5$. How this does not provide an answer? It's a direct answer since it's an elementary math problem. Do I need to explain more than the expression I wrote? $\endgroup$ – Bruno Reis Jun 30 at 1:22
  • $\begingroup$ FYI, that comment is a formatted thing that happens automatically by clicking. I probably did it by mistake, since this is definitely an answer to the question. Will delete. $\endgroup$ – The Count Jun 30 at 2:24
  • $\begingroup$ @TheCount Oh, no problem mate. Thanks! $\endgroup$ – Bruno Reis Jun 30 at 3:45

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