OK, I know it’s an old one, but I love it…..So, there is a frog called Jason. Jason has been a very silly frog and fallen into a well that is 12 feet deep. Now, as you might expect, Jason is eager to get out, but can only jump 3 feet high. Not only that, the walls of well are covered in slime and so he slips down 2 feet each time he lands. So, every jump takes Jason 3 ft up but 2 ft back. How many jumps will Jason have to make to get out of the 12ft well?

Before you ask, Jason does not have access to any springs, ‘Space Hoppers’ (also known as skippyballs, kangaroo balls, bouncers, hippity hips, hop balls, and hoppity hops), or crampons.

The answer to this puzzle, and 100 others,  can be found in a new kindle ebook called PUZZLED, and is available in the UK here and USA here.

1. will says:

i have two solutions that both seem viable. I guess i have to wait to explain them.

2. grejen711 says:

Yes, Will, It’ll depend on how good the catch is on that last jump eh?

3. Fergus Gallagher says:

I know the answer but the question is badly phrased. It doesn’t say whether the jump to 12ft is enough to get him out of the well (i.e., his front legs just touching the rim)

So is the height of his first jump from the “floor” (both legs on the floor) to his front legs or his rear ones? I would argue the answer differs by 1 depending on this assumption.

Another possibility is that he’s clinging to the wall under water at the start, with his front feet at the water’s surface. In this case the nominal answer would get his front feet to the rim and need 1 extra hop to get out.

(I hope I’m just being a pedant and this isn’t supposed to be part of the question or I’m gonna feel pretty dumb.)

4. Ellen says:

I just drew a graph and counted the jumps… but there ‘s probably a catch. And I’m an optimist about the last jump.

5. docpaul says:

I think I know – took maybe 2 seconds. Any way what sort or name is Jason for a frog?

6. If my answer is right, (only took me a few seconds) Everyone using math to work it out are making themselves a lot of work to get an incorrect answer 😉

7. Claire says:

OK I think I have the answer.

I initially thought it was a kind of trick question because the height of the frog isn’t given! Maybe it was a mutant frog exposed to toxic waste and it’s like 10 feet tall already so it only needs 2 jumps!! But that’s my overactive imagination for you! 🙂

8. I’ve seen this before. It’s sneaky, but a little logic and adding up does the trick. It took me less than a minute to come up with a solution and test it.

9. Ellen says:

Well well. I might have a second answer.

10. I’m just going to pop out and find a frog and then dig a well. Theory is all very fine but I do like to see practical proof. Growing the slime might take some time ….. I’ll report back in November ……

11. Gib says:

I think we can assume that his back legs start on the ground, and that his back legs need to be on the surface for him to be “out”.

So, if the well was 1m, and he can jump 1m, then it will take one jump to get out.

It took me 2 seconds to figure out the answer, and yes, I remember the “trick” from when I first heard it years ago…

12. will says:

i actually now have 3 answers, none of which involve maths.

13. iszi says:

If he goes up exactly 12ft does that mean he is free? Or does he need to go over 12ft. Either way, I gots it, but it might take another jump to get outa there.

14. Marc Otway says:

Well, It’s a puzzle. So you can safely assume that the obvious answer of 12 is incorrect. You should think of the answer to the question of “Why would it not take him 12 jumps”

15. maths and science folk immediately look to the ‘boundary conditions’ – then you’ve got it. Again, with a little frog empathy.

16. Just tried googling this, everyone on the interweb seems convinced of “the obvious” maths answer. I’ve got three answers here, none of which involve maths… so is there an actual “right” answer?

17. lflcorreia says:

It took me some minutes but i’ve got it!
I already knew a similar puzzle but involving a snail instead of a frog that during the day climbs a certain amount of a wall but during the night, while he sleeps, he slips down half the amount he climbed and what was asked was if the snail started climbing for example on monday in which day did he reached the top of the wall.

18. RJ says:

I found a solution that seems like common sense, but it assumes that Jason’s final leap allows him to catch the rim of the well and essentially be “out.”

By the way, I only recently found your blog. Since the whole blog thing got started a few years back, this is only the second one I’ve found that has kept me coming back. I’ll have to check out your books.

19. Frank says:

It took me a few seconds to work it out in my head, but I had seen this one before.

20. Ellen says:

I have a third solution as well! One of my solutions now involves ‘maths’, in a very simple way.

21. Rebecca says:

I got an answer, but I know this is a trick question, so I am pretty sure i got it wrong…
It took me about a minute.

22. lipglosser says:

This seems very easy…. which makes me think I’m wrong….
But, if I’m right it only took me a few seconds

23. martina says:

my initial reaction was 12 and then i went through it step by step using my fingers to count the jumps and doing the maths and yeah possible two answers, depending on final jump, neither of which is 12….

24. rares says:

done it in 10 seconds.of course not 12 ffet as almost everyone thinks it is ar forst look

25. rares says:

i meant 12 jumps

26. leigh says:

it took me a second to work the out
12