4

I saw this puzzle many moons ago and so I assumed it would already be on here somewhere. I have looked and not found, though, and so I present to you a puzzle that baffled me when first I saw it.

What number replaces the question mark in the last example and why?

3531 → 0
3597 → 1
3891 → 3
9397 → 2
3869 → 4
2128 → 2
3786 → 3
3506 → 2
2700 → 2
7212 → 0
7205 → 1
2990 → 3
9503 → 2
1057 → 1
1160 → 2

1995 → ?

xnor
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Engineer Toast
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2 Answers2

14

The answer provided by Mathias711 is correct, however there is an alternate and lengthier solution to this problem.

We can assign the number values....

Like from 3531 = 0 and 7212 = 0, we can say that the digits 3,5,1,7& 2 have NO VALUE

Using this information we can get the value of 9

As 3597 = 1, and the fact 3,5&7 have no value, we can say 9=1 (i.e 9 has a value of ONE)

Similarly we can figure out the values of all digits, however we don't need to as we already have enough information to get the answer....

1995= 2 (as 1&5 have no value and 9 has a value of ONE, hence two 9's will be 2)

The Dragonista
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    Excellent mathematical solution. This is the adult-level answer. – Engineer Toast Feb 09 '15 at 14:05
  • +1 for a purely mathematical not-outside-the-box answer. – dmg Feb 09 '15 at 14:05
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    Ironically, using this method, we still have no idea what value: 4444 would be ;) lol – Ditto Feb 09 '15 at 14:24
  • @Ditto But no one cares as it is not in the problem statement. Technically even with the original method, you could not be certain as 8, 6 and 9 have circle(ish) parts, while 4 is more like a triangular. – dmg Feb 09 '15 at 14:41
  • @dmg Exactly!!! :P :) – The Dragonista Feb 12 '15 at 13:25
  • @dmg Areas have rounded or triangular areas are of no concern as the original method counts "enclosed areas" regardless of shape. – Engineer Toast Feb 24 '15 at 17:18
  • @EngineerToast What does "the original method" mean? This solution is as valid as the other one, despite not working for 4s as 4s are not in the problem statement. As far as we are concerned 4 might mean a 4. – dmg Feb 24 '15 at 20:09
  • @dmg I agree that this method is completely valid and not one that I expected. I quoted "original method" from your comment on Feb 9. I had presumed you were talking about the accepted answer. Side note: There is no 4 on purpose because some people write 4 with an open top like an upside-down lowercase h. I didn't want the ambiguity in case someone had their fonts set to that kind of 4. – Engineer Toast Feb 24 '15 at 21:21
4

It is

2

You count the amount of

enclosed areas in the numbers

Mathias711
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  • That certainly didn't take long and this is the kind of elementary answer I expected. – Engineer Toast Feb 09 '15 at 14:02
  • Not sure why the other answer is so much more popular. It's pretty much the same thing as this, but without making the connection with what you're actually counting. – glibdud Feb 23 '15 at 19:51
  • @glibdud The other answer is more mathy. The masses have spoken on which is regarded as more clever. This answer more accurately meets the intent of the question, though. – Engineer Toast Feb 24 '15 at 17:17