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Hi,

I am prepare for a interview. The company usually ask trick question. I got a couple of them from friends and would like to ask for advice from you.

1) There are two poles with same height of 50 ft. The two poles are separated from each other 100ft, and there is a string 100ft long whose ends are tied to tops of the poles. Now try to bring the two poles together until the string touches the ground. The question is: when the string touches the ground, how far apart the two poles from each other?

I know it has something to do with geometry :), but already forget the stuff.

Thanks,

I am prepare for a interview. The company usually ask trick question. I got a couple of them from friends and would like to ask for advice from you.

1) There are two poles with same height of 50 ft. The two poles are separated from each other 100ft, and there is a string 100ft long whose ends are tied to tops of the poles. Now try to bring the two poles together until the string touches the ground. The question is: when the string touches the ground, how far apart the two poles from each other?

I know it has something to do with geometry :), but already forget the stuff.

Thanks,

The whole point of these questions (if there is a point at all) is that you CAN'T prepare for them. If you know the answer in advance, it proves nothing. If you have never heard of a problem anything like it, but are able to come up with an outside-the-box solution, it could indicate something about your problem-solving ability.

So here is the secret.... if you have heard the answer to any of these screwball querstions, don't *DO NOT* immediately write it down. Instead take a long time with it... draw a diagram. Show a matrix of possibilities... THEN pretend to think of the answer with a flash of intuition.

Before going to the interview, practice saying "ahhh HA!" in the mirror. Maybe the occcasional "Eureka!" would be ok, but I'd opt for spending the most time practicing the "puzzled-expresssion-turns

A perfectly-executed "squenched-up-brow-resolve

I agree with Dan.

Any quick answer could also indicate lack of additional experience that could give one pause to remember what the answer was, leading to conclusion of being too green.

Personally, I distaste such question any interview.

There is book called" How do you move Mount Fiji?".

Puzzle for superBrain

Mind teasers are good books.

Hope this help

Good luck

http://mathworld.wolfram.com/Catenary.html

You start with this situation - a rectange 50 ft high and 100 ft wide.

---------------

| |

| | 50 ft

| |

---------------

100 ft

After pulling the string, assuming the poles do not bend and the string does not stretch. You have two equilateral (not right angled) triangles.

/\ /\

/ \ / \

/ \/ \

-----------

The poles are still 50 ft long. The string touches the ground mid way between the poles, so it is 50 ft from the base of each pole. The length of string from the ground to the top of each pole is 50 ft (half the length of the original string on each side).

So you have two equilateral triangles with sides of 50 ft touching each other. From here it's pretty easy to see that the tops of the triangles are 50 ft apart.

jhshukla, you would have a catenary if the string was hanging freely, but the question says you pull it, so it effectively becomes a straight line (unless it’s really heavy string).

Guess I won't be hiring at EE just yet. :)

Guess I owe you an apology. I've just noticed the author's addendum about the poles remaining perpendicular. It's a strange constraint, but legal in the puzzle universe, and in that case your answer is dead on. That will teach me to read all the posts properly before responding in future.

It said the poles remain perpendicular to the ground, it didn't say that the base of the poles remained 100 ft from each other.

---------------

| |

| | 50 ft

| |

---------------

100 ft

Becomes:

---------------

||

|| 50 ft

||

---------------

100 ft

yes, very tricky.

saw this one .....which made me join this grp!!

bcoz the solution is very simple

Essentially the poles on both end would bend as a part of circle as both the distance of base of pole and it's tip from the centre would be 50 ft .

using some basic trignometry

the distance = 2 x 50 Cos(180/pi)

Ans = 53.98 ft

Welcome to the group.

You didn't read the whole thread. Look at the first comment by xl2003 after asking the question. Both poles remain perpendicular. Go back 3-4 posts for the entire explanantion.

read the question again. it asks you to bring the poles together, not to pull the string.

1) There are two poles with same height of 50 ft. The two poles are separated from each other 100ft, and there is a string 100ft long whose ends are tied to tops of the poles. Now try to bring the two poles together until the string touches the ground. The question is: when the string touches the ground, how far apart the two poles from each other?

> you need atleast a piece of string 100' 1"

let's use glue.

actually, it may be impossible due to another reason. the rope has some non-zero thickness. so two halves of the rope would be some distance apart and the bend at the bottom has some finite curvature. depending on the stiffness of the rope, it could look like:

||

U

____

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assume that the distance between two poles is x. We have a right triangle (???), whose hypotenuse is half of the string and the two legs are the pole and x/2. Since height(the hypotenuse) = 1/2 the string = height(the pole) -> x/2= 0 -> x=0-> QED :)