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Topic: simple math riddle: pole in mud and water (Read 3954 times) |
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BMAD
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simple math riddle: pole in mud and water
« on: Jun 2nd, 2014, 5:44pm » |
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There is a pole in a lake. One half of the pole is in the ground, another one third is covered by water and eight feet is out of the water. What is the total length of the pole in feet?
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dudiobugtron
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Re: simple math riddle: pole in mud and water
« Reply #1 on: Jun 3rd, 2014, 12:25am » |
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It is simple if you think of it purely mathematically, but if you try to visualise it, the way the fractions relate is pretty deceptive.
But anyway, hint:
using fractions, 1/2 + 1/3 = ?
And answer:
1/6 of the pole is sticking out of the water. 6*8=48. So, the pole is 48' long.
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BMAD
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Re: simple math riddle: pole in mud and water
« Reply #2 on: Jun 3rd, 2014, 4:14am » |
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I disagree
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Grimbal
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Re: simple math riddle: pole in mud and water
« Reply #3 on: Jun 3rd, 2014, 6:14am » |
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Is "in the ground" also "out of the water"?
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rmsgrey
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Re: simple math riddle: pole in mud and water
« Reply #4 on: Jun 3rd, 2014, 6:28am » |
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I get three different numbers, depending on the interpretation - dudiobugtron and Grimbal have given two of them. The third: "another third" is a third of the remainder, not of the whole pole.
The arithmetic is straight-forward for all three cases.
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JiNbOtAk
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Re: simple math riddle: pole in mud and water
« Reply #5 on: Jun 3rd, 2014, 7:06pm » |
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The first interpretation :
l = 1/2l + 1/3l + 8ft
l = 5/6l + 8ft
1/6l = 8ft
l = 48 ft ---> (the answer given by dudiobugtron)
Second intepretation :
1/3l in the water, which means 2/3l is out of water.
Thus 2/3l = 8 ft
l = 12 ft
1/2l = 6ft is in the ground,
1/3l = 4 ft is covered by water and
1/6l = 2 ft is 'out' of the water ----> (Grimbal's version)
Third interpretation :
1/2l in water
1/3 of the remainder, i.e. 1/3 of 1/2l is in the water. 8ft is out of the water. This becomes :
1/2l + (1/3 of 1/2l) + 8ft = l
1/2l + 1/6l + 8ft = l
2/3l + 8ft = l
l = 24ft
12ft - in the ground
4 ft - in the water
8 ft - out of the water ---> (rmsgrey's interpretation)
Fourth Approach (combination of Grimbal's and rmsgrey's approach, one third of the remainder AND out of water also include in the ground).
1/3 of remainder is in water, i.e. 1/3 of 1/2l
= 1/6l
Thus 5/6l is out of water.
5/6l = 8ft
l = 9.6 ft
4.8 ft is in the ground
1.6 ft is in the water
3.2 ft is visible above water.
Any other possible interpretation ?
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| « Last Edit: Jun 3rd, 2014, 8:19pm by JiNbOtAk » |
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Grimbal
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Re: simple math riddle: pole in mud and water
« Reply #6 on: Jun 4th, 2014, 1:50am » |
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I am curious why BMAD disagrees.
The first interpretation is what the most commun use of english implies. You have another interpretation?
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0.999...
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Another interpretation.
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BMAD
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Re: simple math riddle: pole in mud and water
« Reply #8 on: Jun 4th, 2014, 3:48am » |
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I was in line with jinbotaks second interpretation. .12
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BMAD
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Re: simple math riddle: pole in mud and water
« Reply #9 on: Jun 4th, 2014, 4:43am » |
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If 1/3 is in water then 2/3 must not be. Simple algebra then would suggest it be 12 feet.
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Grimbal
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Re: simple math riddle: pole in mud and water
« Reply #10 on: Jun 4th, 2014, 7:19am » |
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I see.
But in the context of a pole in a lake, "out of the water" is understood as "above water level".
The phrasing is intentionally misleading.
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| « Last Edit: Jun 4th, 2014, 9:39am by Grimbal » |
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BMAD
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Re: simple math riddle: pole in mud and water
« Reply #11 on: Jun 4th, 2014, 7:51am » |
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on Jun 4th, 2014, 7:19am, Grimbal wrote:
Not nice, especially for us non - native English speakers. 
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rmsgrey
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Re: simple math riddle: pole in mud and water
« Reply #12 on: Jun 4th, 2014, 8:03am » |
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on Jun 4th, 2014, 7:51am, BMAD wrote:
Not nice, especially for us non - native English speakers. |
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The "gry" riddle is notorious for being mistold. A "correct" version is:
"'hungry' and 'angry' are both words that end with 'gry'. There are three common words in 'the English language'. What is the third?"
Obviously, when spoken, the quotes round 'the English language' are not apparent. The key to the riddle is that the -gry sentence is purely there as a distraction (which is of questionable legitimacy in the first place). When told wrongly (as in the xkcd strip) the official solution doesn't actually fit the riddle at all.
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dudiobugtron
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Re: simple math riddle: pole in mud and water
« Reply #13 on: Jun 4th, 2014, 1:04pm » |
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Another objection to the 'in the ground' = 'out of the water' interpretation, is that much of the ground under a lake will be very wet.
However, and objection to my interpretation is that you are unlikely to find a lake where you can dig a pole 24 feet into the lake bed.
on Jun 4th, 2014, 3:20am, 0.999... wrote:
With this interpretation (some of the ground is 'in the water', and some of the ground isn't), we don't have enough information to solve it.
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JiNbOtAk
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Re: simple math riddle: pole in mud and water
« Reply #14 on: Jun 5th, 2014, 5:16am » |
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on Jun 4th, 2014, 1:04pm, dudiobugtron wrote:| However, and objection to my interpretation is that you are unlikely to find a lake where you can dig a pole 24 feet into the lake.. |
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Why not? 24 feet is not that deep. A piling machine could definitely achieve that depth.
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UgoLocal02
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Re: simple math riddle: pole in mud and water
« Reply #15 on: Jun 11th, 2014, 11:00pm » |
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I think the right answer to this riddle is 12 feet.
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Annettagiles
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Re: simple math riddle: pole in mud and water
« Reply #16 on: Oct 21st, 2014, 4:40am » |
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could you please post a image which will be very helpful for me to give you a solution
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