The 33 1/3 second mystery #33
 

Put on your math hats, kids!

What is the next number in the sequence: 13, 15, 21, 23, 27

Explain your answer.

EDIT: nevermind, had no clue what i was talking about.

the # is 13.

cuz i suck at math....and that's a good number.

28...

5 numbers between the first set, 3 numbers between the second set, ergo, 1 number between the third set...

nevermind

nevermind, 13, and 28 are all incorrect.

29

+2, +6, +2, +4..... 2 seems the next value by which to increase the last number in the series

29

same reasoning as fernweh

Such is the beauty of mathematics. 29 although not the answer, is integral to the answer.

31

The numbers in the sequence are
13 15 21 27
They can be expressed as the prime numbers [11 13 17 19 23] added to [2 2 4 4 4]. If we add the next sequential prime number to the first matrix, it would be 27. Of the second matrix, two repeats itself twice, so four should repeat itself four times, so let's add four to it. 27+4=31, the next number in the sequence.

I'm probably making this problem waaaay more complicated than it should be, but still... :)

27 isn't a prime number.

29 plus 4 is 33, but I mean can you just assume 4 will repeat itself four times.

Maybe, it's a prime number and then the next two odd multiples of 3, then the next prime number, then the next two multiples of three. In this case the answer would still be 33.

Im gonna guess 4 cause thats the number of advil I took after reading this.

Noahfor--
Ok ok my bad... but we know that 29 is "integral to the answer" so then I bet you're right... I vote 33 too :)

33 isn't it. You folks are soo close to the answer, it could bite you! Think outside the box ;)

Go back to fernweh's first post in this thread, make a correction, and you might get the answer. ;)

My bad-that was the second post by fernweh. :o

35?

Since we know 29 is "integral to the answer" and it's the next prime number in the sequence, we know that the question is now which number comes next in THIS sequence: [2, 2, 4, 4, 4] and we're gonna add that to 29. It looks like it would be an even number, and 6 is the next one, so.... 35? :)

35 is indeed the correct answer. :thumbsup: The key to this puzzle is looking at different numerical bases. Were it constructed in binary or hexidecimal, that would have been a dead giveaway. Instead, I chose octal, and started with two integer primes, where 11=13, 13=15, 17=21, 19=23, 23=27, and 29=35.

I was all but certain you folks had it cracked with the 2,4 logic postings starting on the 16th.

An eight-legged fuzzy bunny to fernweh:D