5
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You can use $+, -, \times, $ or $/$ (namely $\div$).

Use all five numbers (20, 17, 16, 8, and 7) only once to make $9$.

From what I've been told there are $4$ answers. The only one I've been able to figure out is:

$$\Bigg((17-7)\times\left(\frac{20}{8}\right)\Bigg)-16=9$$

Any help would be appreciated.

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  • 1
    $\begingroup$ Are the given numbers supposed to be used only once ? $\endgroup$ – Mea Culpa Nay Oct 2 '18 at 1:03
  • $\begingroup$ is concatenation allowed? $\endgroup$ – Shahriar Mahmud Sajid Oct 2 '18 at 4:11
  • $\begingroup$ You can only use them once. I don't know what concatenation is but I would assume no. I was told addition, subtraction, multiplication, and division. $\endgroup$ – Nate Smith Oct 2 '18 at 14:43
  • $\begingroup$ Nice. I've been working on this thing for weeks. $\endgroup$ – Nate Smith Oct 3 '18 at 19:07
4
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Here is one:

$$\Bigg((20-7)\times\left(\frac{16}{8}\right)\Bigg)-17=9$$

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4
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Here are four answers:

  1. $20\times\frac{17-7}{8}-16$

  2. $\frac{20\times(16-8)-7}{17}$

  3. $(20-7)\times\frac{16}{8}-17$

  4. $167+20-178$

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  • $\begingroup$ $1$ and $3$ are the same equation $\endgroup$ – Shahriar Mahmud Sajid Oct 2 '18 at 5:40
  • $\begingroup$ @ShahriarMahmudSajid fixed it. $\endgroup$ – Oray Oct 2 '18 at 5:40
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    $\begingroup$ not sure if concatenation is allowed, asked the OP, didn't get an answer yet. $\endgroup$ – Shahriar Mahmud Sajid Oct 2 '18 at 5:49
  • $\begingroup$ Concatenation is not allowed. $\endgroup$ – Nate Smith Oct 4 '18 at 13:16
  • $\begingroup$ @NateSmith these are only solutions, I did it with computer, checked all solutions. so if concatenation is not allowed, there are 3 answers. $\endgroup$ – Oray Oct 4 '18 at 13:17

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