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100 / 5 = 14 
30 + 30 = 60
50 * 2 = 120
100 - 5 = ?

What is the answer, that should be in place of the question mark?

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  • $\begingroup$ I think it's 64. Pressed for time, no time to give informative answer, so it;s a comment. $\endgroup$ – ObviouslyJake Nov 14 '16 at 15:06
  • $\begingroup$ I am unsure if i should say if it was correct or incorrect in the comments. Could you also elaborate a bit more later on on how you go there? $\endgroup$ – Gertjan Brouwer Nov 14 '16 at 15:09
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The answer is

73

The trick is

All numbers are given in Octal

Some deductions I made:

30+30 works, so the math is probably right in a different base,
50*2=120 got me to Octal, which confirmed my suspicion based on the question title.

Incidentally, 100/5=14

Works in Integer Division, in regular mathematical division, it results in a remainder.

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  • $\begingroup$ ha, ninja'ed because I was taking the extra time to explain that the division on the first line had to be taken as truncating :-). $\endgroup$ – Gareth McCaughan Nov 14 '16 at 15:09
  • $\begingroup$ Oh, good point, I'm kinda used to Computer-style division, I'll comment that in $\endgroup$ – Sconibulus Nov 14 '16 at 15:12
  • $\begingroup$ This is indeed right $\endgroup$ – Gertjan Brouwer Nov 14 '16 at 15:13

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