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Ship Ladder - Back to the Logic Puzzles

A ladder hangs over the side of a ship anchored in a port. The bottom rung touches the water. The distance between rungs is 20 cm and the length of the ladder is 180 cm. The tide is rising at the rate of 15 cm each hour.

When will the water reach the seventh rung from the top?

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If the tide is raising water, then it is raising the ship on water, too. So water will reach still the first rung.

A ship anchored in a port has a ladder (beginning and ending with a tave), where the bottom tave touches the water. The distance between taves is 20 cm and the length of the ladder is 180 cm. The tide is rising at the speed of 15 cm each hour. When will the water be on the third tave from the top?

Edit: tave = rung

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• 2 months later...
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This rather depends on the tension on the Anchor, If the Ship is Anchored with no slack then it can not rise with the tide, and in this instance it would take 10 hours and 40 minutes to reach the 8 rung (third from the top).

Only if there is enough slack to allow a full 180cm rise in the tide could you answer be correct.

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This rather depends on the tension on the Anchor, If the Ship is Anchored with no slack then it can not rise with the tide, and in this instance it would take 10 hours and 40 minutes to reach the 8 rung (third from the top).

Only if there is enough slack to allow a full 180cm rise in the tide could you answer be correct.

I have yet to know any decent seaman anchor a ship without allowing for tide...

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Ok first of all you got me. And so the math I did is irrelevant, but since others worked it out too, I am confused as to how you got to the answer of 10 hours 40 minutes to reach the 8th stave. As I did the math, the ladder is 180 cm long and the distance between staves is 20 cm. 180 / 20 = 9 staves. So if we are trying to get the the third from the top our target stave would be number seven not number eight.

If the above math is correct then the target height is 120 cm (remeber the number 1 stave is at 0 cm not at 20 cm)

If the target height is 120 cm and the tide rises at 15 cm per hour then it would take eight hours to reach the number seven stave (120/15).

Just assume the tide rises and the boat doesn't is my math faulty?

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Sharkmateher - Your math is wrong, as you mention the bottom stave is zero so to get to 180 you need 10 staves not 9 (see below)

180 --- 10

160 --- 9

140 --- 8

120 --- 7

100 --- 6

80 --- 5

60 --- 4

40 --- 3

20 --- 2

0 --- 1

Larryhl. I was playing devil's advocate, nowhere in the puzzle does it say that the ship is anchored by a good saeman! But I agree it is likely to have enough slack, for the original answer to be correct.

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• 2 weeks later...

My initial thoughts was that it depends on

-how far in the tide is already

-where the boat is docked

-what phase the moon is in

...since the degree of the change of tide changes dramatically with location and time of year.

But of course this doesn't matter based on the answer...just thought it would be something else to think about:)

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• 2 weeks later...

When the ship sinks.

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Given that an anchor prevents a ship from moving by dragging through the mud, and not by physically attaching the ship to the bottom of the harbor; And given that most ships have no problem floating with their anchor(s) on deck; I propose that the ship would simply rise with the tide pulling the anchor off the bottom of the harbor when the slack runs out. So it doesn't really matter if there is slack in the anchor chain or not.

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NEVER...the boat wouldn't have an anchor heavy enough to hold it in place with the raising tide or the boat wouldn't be able to float with the anchor up...

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• 2 weeks later...

I agree with the answer as given. However, since the boat is in port, it could be empty at the time the bottom tave is touching the water, which would make a certain amount of sense. As the ship is loaded, it could sink down to the point that the third tave from the top is touching the water. Of course, there is not enough information given to properly answer the question more precisely that saying "when it is loaded".

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• 4 weeks later...

Hi all,

Perhaps the answer is never or only when the ship sinks, or during some major weather event, because, the tide only ever rises for six hours, so, whether the boat is anchored or not, the water will never reach the third down under normal circumstances.

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Whether or not the boat rises, since there are 2 high tides and two low tides per 24 hours, the time between low tide and high tide is never more than 6 hours, give or take. Since to reach the 3rd highest rung would take over 8 hours, it could not possibly reach it at the rate described.

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I hate that the person before me said my thoughts ... urg

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never

the ship will rise with the tide

cai

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• 4 weeks later...

I was also tricked into doing the unnecessary math, but still got a different number than all y'all. One guy posted the following:

180 --- 10

160 --- 9

140 --- 8

120 --- 7

100 --- 6

80 --- 5

60 --- 4

40 --- 3

20 --- 2

0 --- 1

So the third tave from the top (#8) is at a height of 140cm divided by 15 mins per hour leaves an answer of 9hrs 20 mins. Of course, we all know the tide would already be going down again and the boat wouldn't sink...but just testing the math part...

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• 3 weeks later...
When the ship sinks.

The solution is damn right but another logically right answer and totally humorous answer was da one given by beaker_reborn!!

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Fooled me too! But since I did the math (assuming the ship doesn't move) I also got 9:20

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I think you guys are missing the point. The third stave from the top is NOT # 8, it's #7. If #10 is the top, then it follows that # 9 is the first from the top, #8 the second, and 7 the third.

It's the same as a race. There's a winner and then there are runner-ups. The first runner-up is not the winner (top stave), it is the one that directly follows.

If that's the case, the correct math answer would be 8 hrs [120cm/(15cm/hr)].

It's all irrelavent, I concede, considering the correct math answer is not feasible anyway.

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I think you guys are missing the point. The third stave from the top is NOT # 8, it's #7. If #10 is the top, then it follows that # 9 is the first from the top, #8 the second, and 7 the third.

I think that saying #8 is third from the top is true. We're saying it's the 3rd rung from the top, not the 3rd rung from the top rung. Likewise, #3 would be the 3rd from the ground, but only the 2nd from the bottom rung, even though we agree it doesn't matter in this puzzle.

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• 4 weeks later...

Call me goofy fellas, but if the ship is floating, hence being anchored to prevent it from drifting away, then the rising tide will also raise the ship the same amount as the rising of the tide in terms of distance from the sea bottom.

The bottom tave will always be in the same position unless the ship sinks or increases/decreases its draft due to cargo operations or ballasting/deballasting.

As for the anchor holding a ship to the bottom if it were to come to a short stay; the bouyancy of the vessel is sufficient to carry the anchor as part of its compliment. How on Earth is it going to hold it to the bottom?

Common sense prevails at every turn. Congrats to those who posted accordingly.

Kurt Niemann, MKC

Chief Petty Officer United States Coast Guard, 16 years.

"Altus Tendo"

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never, unless the boat is tethered to the floor of the harbor.

Peace

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Never. The ship will simply rise with the water and the ladder with ship.

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love this riddle... I showed it to my eighth grade class last year. Nobody got it. And I mean nobody

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Assuming that the ship was tethered and wouldn't rise with the tide, the answer is still never because tides change roughly every 6 hrs anyway and all otherwise 'valid' solutions take longer :-D So, (still assuming the ship doesn't move with the tide) the answer would be something like when the hurricane (or Typhoon) hits.

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Ships are bouyant. the ship will rise with the tide. anchors hold ships still.not down. did you ever hear of a ship sinking because a green sailor tried to drop anchor in water that their chain didn't reach the bottom??

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