How long until the water reaches the top step on this 5th grade brain teaser?

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Discussion Overview

The discussion revolves around a brain teaser involving a boat, a ladder, and rising water levels due to a tide. Participants explore how long it would take for the water to reach the top step of the ladder, considering various interpretations of the problem and the physical setup.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Mathematical reasoning

Main Points Raised

  • Some participants suggest it would take 16 minutes for the water to reach the top step.
  • Others propose a shorter time of 12 minutes, arguing that the problem is straightforward.
  • One participant questions the setup of the boat, suggesting that if the boat is not floating, the tide would affect the ladder's position differently.
  • Another participant states that the water will never reach the top step because the boat rises with the tide, maintaining the same distance from the water level.
  • A few participants mention the use of differential equations to analyze the problem, indicating a more complex mathematical approach.
  • Some express confusion about the problem's requirements and whether additional information is needed.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the time it would take for the water to reach the top step, with no consensus reached. Some believe the water will never reach the top step due to the boat's rising position, while others provide specific time estimates.

Contextual Notes

Assumptions about the boat's position (floating vs. docked) and the interpretation of the problem are not fully resolved, leading to different conclusions among participants.

Who May Find This Useful

This discussion may be of interest to those exploring problem-solving strategies in physics, particularly in relation to buoyancy and relative motion, as well as those interested in mathematical modeling of real-world scenarios.

physicsuser
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A boat is docked at a shore. A ladder is hanged from top of the boat So that the last step is touching the water. The distance between steps is 20 cm and there are 4 steps in the ladder. A tide is raising the water-level 5 cm a min. How long will it take for the water to reach the top step.
 
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Phew ! :confused: That's a real toughie ! Luckily, I'm not in the 5th grade. :wink: :biggrin:

Otherwise, I may have complained about insufficient information ! :rolleyes:
 
16 minutes
 
gabe said:
16 minutes

I guess you're not in the 5th grade either, eh ?
 
I'd say a 5th grader was trying to get his homework question answered. Hmm, smart enough to trick you but not smart enough to do the problem.

Ohh, and it is only 12 minutes.
 
Last edited:
ExtravagantDreams said:
I'd say a 5th grader was trying to get his homework question answered. Hmm, smart enough to trick you but not smart enough to do the problem.

Ohh, and it is only 12 minutes.

That would be the correct wrong-answer !
 
Last edited:
how is the boat docked? if it is far up on shore, not floating, and the tide level won't affect its position then i'd agree with the 12 minutes. however, if the boat is docked such that it is floating, then the tide won't move relative to the ladder.
 
its a differential equation!

i donno :D
 
The answer seems obvious to me. No math needed. But then I live down the street from a Marina.

(am I missing something?)
 
  • #10
Gokul43201 said:
That would be the correct wrong-answer !

Man I hate those
 
  • #11
Math Is Hard said:
The answer seems obvious to me. No math needed. But then I live down the street from a Marina.

(am I missing something?)

(No, you're not.)
 
  • #12
it will never reach the top step as the boat also rises with the tide.
 
  • #13
vikasj007 said:
it will never reach the top step as the boat also rises with the tide.

indeed. :smile:
 
  • #14
notice these two geeks used relativity for a 5th grade problem :-p


i still think there's a differential equation..
 
  • #15
cronxeh said:
notice these two geeks used relativity for a 5th grade problem :-p


i still think there's a differential equation..

Yes there is :

dx/dt = 5 = dy/dt

x(t=0) = 0

y(t=0) = 60

find t when x=y.
 
  • #16
hahaha funny
the boat will just rise so the water never rises up the ladder all the way-- unless the boat sinks
 
  • #17
well i am in 5th grade so probably wrong, but wouldn't the ladder rise with the boat
just a guess:biggrin:
 
  • #18
Tom McCurdy said:
hahaha funny
the boat will just rise so the water never rises up the ladder all the way-- unless the boat sinks

:smile: :smile: :smile:
 

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