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

  • 3
    $\begingroup$ 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 May 11 '16 at 3:56
  • 14
    $\begingroup$ There's 10 kinds of people in the world. Those who understand binary and those who don't. $\endgroup$ – Johannes Pille May 11 '16 at 8:09
  • 5
    $\begingroup$ @JohannesPille and those who understand Gray code. $\endgroup$ – Pierre Arlaud May 11 '16 at 8:33
  • 34
    $\begingroup$ There are 10 kinds of people - those who understand ternary, those who don't, and those who mistake it for binary! $\endgroup$ – Alexander May 11 '16 at 9:18
  • 3
    $\begingroup$ Funny thing is, I catched this instant aswell, but by catching a hint that actually wasn't one.... I read "turing" ^^ $\endgroup$ – Zaibis May 11 '16 at 15:15

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.

  • $\begingroup$ Oh.. Super fast ! I was typing the same :) $\endgroup$ – Arun Xavier May 11 '16 at 3:58
  • 1
    $\begingroup$ Ninja'd by the pro! $\endgroup$ – KoA May 11 '16 at 3:59
  • $\begingroup$ @ᴊᴀᴠʏ Me too, but at same time we post; after a few mins we don't :) $\endgroup$ – Jonathan Allan May 11 '16 at 4:00
  • $\begingroup$ Is the LSB usually 'last' ? I guess the hint defines it, but it took the hint... $\endgroup$ – Lamar Latrell May 11 '16 at 5:19
  • 1
    $\begingroup$ @Lamar: Yes, just like the least significant digit is last in base ten. $\endgroup$ – Deusovi May 11 '16 at 5:20

Today you are turning



you are lighting your candles in binary, $11110 = 30; 11111 = 31; 100000 = 32$

  • $\begingroup$ Ninja'd you again. :P $\endgroup$ – Deusovi May 11 '16 at 4:00
  • $\begingroup$ @Deusovi Well you got an ^vote from me :) $\endgroup$ – Jonathan Allan May 11 '16 at 4:01

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)


You're turning


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


and only light the first candle and not the other 5.


protected by Community May 11 '16 at 10:13

Thank you for your interest in this question. Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).

Would you like to answer one of these unanswered questions instead?

Not the answer you're looking for? Browse other questions tagged or ask your own question.