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

[physicsuser]

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.

 

[Gokul43201]

Phew ! That's a real toughie ! Luckily, I'm not in the 5th grade.

Otherwise, I may have complained about insufficient information !

 

[gabe]

16 minutes

 

[Gokul43201]

16 minutes

I guess you're not in the 5th grade either, eh ?

 

[ExtravagantDreams]

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.

 

[Gokul43201]

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 !

 

[dusty8683]

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.

 

[cronxeh]

its a differential equation!

i donno :D

 

[Math Is Hard]

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

(am I missing something?)

 

[ExtravagantDreams]

That would be the correct wrong-answer !

Man I hate those

 

[Gokul43201]

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.)

 

[vikasj007]

it will never reach the top step as the boat also rises with the tide.

 

[physicsuser]

it will never reach the top step as the boat also rises with the tide.

indeed.

 

[cronxeh]

notice these two geeks used relativity for a 5th grade problem


i still think there's a differential equation..

 

[Gokul43201]

notice these two geeks used relativity for a 5th grade problem


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.

 

[Tom McCurdy]

hahaha funny
the boat will just rise so the water never rises up the ladder all the way-- unless the boat sinks

 

[fail man130]

well i am in 5th grade so probably wrong, but wouldn't the ladder rise with the boat
just a guess

 

[ƒ(x)]

hahaha funny
the boat will just rise so the water never rises up the ladder all the way-- unless the boat sinks