It is my birthday today
Last year I had 5 candles
4 were lit the last was not
But today, I'll light them all
How old am I turning today?
HINT: I am not turning 5 today and...
Next year I'll have 6 candles, but I'll only light the first
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4$\begingroup$ Hey, welcome to Puzzling! This is a good first puzzle but I highly recommend holding off on giving hints - often you'll find out you don't need them. $\endgroup$– Deusovi ♦Commented May 11, 2016 at 3:56
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17$\begingroup$ There's 10 kinds of people in the world. Those who understand binary and those who don't. $\endgroup$– Johannes PilleCommented May 11, 2016 at 8:09
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5$\begingroup$ @JohannesPille and those who understand Gray code. $\endgroup$– Pierre ArlaudCommented May 11, 2016 at 8:33
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42$\begingroup$ There are 10 kinds of people - those who understand ternary, those who don't, and those who mistake it for binary! $\endgroup$– AlexanderCommented May 11, 2016 at 9:18
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3$\begingroup$ Funny thing is, I catched this instant aswell, but by catching a hint that actually wasn't one.... I read "turing" ^^ $\endgroup$– ZaibisCommented May 11, 2016 at 15:15
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4 Answers
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You're turning
11111 (Or 31)! This is because you light your candles in binary: last year you turned 30 (11110) so you only lit the first four candles.
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$\begingroup$ Oh.. Super fast ! I was typing the same :) $\endgroup$ Commented May 11, 2016 at 3:58
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$\begingroup$ @ᴊᴀᴠʏ Me too, but at same time we post; after a few mins we don't :) $\endgroup$ Commented May 11, 2016 at 4:00
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1$\begingroup$ Is the LSB usually 'last' ? I guess the hint defines it, but it took the hint... $\endgroup$ Commented May 11, 2016 at 5:19
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2$\begingroup$ @Lamar: Yes, just like the least significant digit is last in base ten. $\endgroup$– Deusovi ♦Commented May 11, 2016 at 5:20
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Today you are turning
31
Since
you are lighting your candles in binary, $11110 = 30; 11111 = 31; 100000 = 32$
answered May 11, 2016 at 3:59
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1$\begingroup$ @Deusovi Well you got an ^vote from me :) $\endgroup$ Commented May 11, 2016 at 4:01
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I've got a different solution, that is very close to the current one, but a little bit different. (and fits of course)
He is turning
30. Every candle that is lit stands for 6 years. Every candle that is not lit stands for 5 years. (5 candles lit is 5x6=30) And next year he becomes 31 (1 candle lit, 5 not. 1x6+5x5=31)
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You're turning
31
Since the analogy is in
binary and the candles represent face values of the numbers,
you light the first 4
Next year you'll turn
32
and only light the first candle and not the other 5.
