Braingle: 'Poor Frog' Brain Teaser

Poor Frog

Math brain teasers require computations to solve.

Puzzle ID:	#758
Fun:	(2.42)
Difficulty:	(1.38)
Category:	Math
Submitted By:	beans
Corrected By:	MarcM1098

A frog fell into a well that was 12 feet deep. He could jump three feet, but every time he did, he would fall back two feet. How many times did the frog have to jump before he got out of the well?

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Comments

starman Sep 17, 2001	Ten is the right answer but I believe on the tenth jump he is starting from 9 and jumping to the top at 12 for what it's worth. (The first jump starts at 0 feet and ends at 1, the second jump starts at 1 and ends at 2 ... the 10th jump starts at 9 and would end at 10 except he reaches the top instead. Still a fun teaser. Thanks.
mrice Oct 02, 2001	starman, If the well is 12 feet deep and you start counting at "zero", then the top of the well is at 11. Therefore, the 10th jump still takes the frog one foot above the top.
peppermintwist Jul 09, 2002	I'm confused, if he jumped 3 feet and fell 2 feet, wouldn't that mean he only gained a foot? Could someone please help me? I'm sure the answer you have is right, but I don't see why.... I stink at math. Thanks!
SPUTNIK2 Feb 04, 2006	that was kinda mind boggling, but that what I'm here for! Great teaser, thanks!
paul726 Mar 04, 2006	Of course his initial position is 0 feet, he's at the bottom of the well! So, each jump brings him up three feet, but he slides down two for a net gain of one foot. This procedes thus for nine jumps. The ninth jump, which started at the eight foot mark, takes the frog up to eleven feet, from which he slides back to nine. The tenth jump then takes him up three more feet, to the twelve foot mark, where, presumably, he catches the lip of the well and pulls himself out without sliding back at all. Ten jumps is correct, but the tenth takes him to exactly the height of the well, not above as the answer initially states.
LeafFan4life Mar 06, 2007	actually this is impossible because he would still fall after he jumps so he would start at the bottom again!
pating Jun 20, 2007	did your brain fell into the well as well? too bad coz your brain cant jump.
Jimbo Mar 28, 2009	An oldy but a goody! (He doesn't have to get above the well but just out. Presumably the top of the well is out)