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You are heading to your hotel room but forget your room number.
Try to check the key card but the digits are blurred
You call to hotel desk info and a nerdy bell boy tell you:

  • Your room have 4 digits
  • the digits are different
  • the digits are in an increasing order
  • the product of the first two is the sum of the last two.

What is your room number?

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  • $\begingroup$ Also I found three possible answers... $\endgroup$
    – user88
    Commented Apr 17, 2015 at 22:12
  • $\begingroup$ My bad, i only found one when made it. $\endgroup$
    – Alberto Ramos
    Commented Apr 17, 2015 at 22:24
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    $\begingroup$ Perhaps this hotel only has 3568 rooms. $\endgroup$
    – Ayefork
    Commented Apr 17, 2015 at 22:25
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    $\begingroup$ @Ayefork Or only 34 floors. $\endgroup$
    – user88
    Commented Apr 17, 2015 at 23:58

2 Answers 2

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The room number is 3457, 3569, or 3578. 3 × 4 = 5 + 7, and 3 × 5 = 6 + 9 or 7 + 8.

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The answers are 3457,3569 & 3578. Calculated using brute force: http://ideone.com/yD3RXL

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  • $\begingroup$ That's a rather inefficient piece of code, though it does the job in this case. $\endgroup$
    – Rohcana
    Commented Sep 22, 2015 at 14:03

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