"Four people are in a room. Six people leave. How many people have to re-enter the room for it to be empty?"

harpazo

harpazo

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Four people are in a room. Six people leave. How many people have to re-enter the room for it to be empty?

Solution:

The answer should be 0. If anyone re-enters the room, it won't be empty.

Yes?
 
Last edited:
Maybe. It's true that if anyone re-enters the room it can, by definition, no longer be considered empty. However, given the impossible nature of the problem I suspect the answer's actually 2... I think it's meant to be the sort of problem where you don't think and just roll with it, never stopping to question how six people can leave a room that only four people were in, or how the room can then contain -2 people. Or maybe it's just a bad question. Who really knows?
 
ksdhart2 said:
Maybe. It's true that if anyone re-enters the room it can, by definition, no longer be considered empty. However, given the impossible nature of the problem I suspect the answer's actually 2... I think it's meant to be the sort of problem where you don't think and just roll with it, never stopping to question how six people can leave a room that only four people were in, or how the room can then contain -2 people. Or maybe it's just a bad question. Who really knows?
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Just another senseless Common Core math problem to make our students smarter. Yeah right....
 
The biggest trouble with the Common Core set of standards is simply that it has to be implemented by fallible human beings. The standards themselves aren't so bad, and many of them even make sense. It's just that very few people have ever seemed to actually get it right so far. It's a sad state of affairs that many elementary/middle school teachers have only a very basic grasp of the material themselves - they know just enough to teach it but nothing more. I recall once asking my 9th grade math teacher if there was a method of calculating square roots without a calculator and she said there wasn't... but there MUST be such a method, or else how could anyone ever program a calculator to do it in the first place, black magic?

Add to this the fact that the teachers learned their math using entirely different methods and entirely different standards and curriculums, you have teachers who have to essentially re-learn all of this "new math" themselves and then try to pass this information on to students. It's no wonder it turned out to be hot garbage.
 
harpazo said:
Four people are in a room. Six people leave....
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In my opinion, the correct answer, at this point, is:

Your question has a terminal fallacy. Please restate the actual intent after repair.

If a teacher of my children insisted it was a valid problem statement and had a numeric answer, said teacher would hear it from me. Additional resistance would result in supervisors' attention and perhaps alerts to professional organization.
 
What is lacking is information on where the question originated. If it is an exercise from a math class, that's one thing. But it happens that I ran across a joke just last night that amounts to the same thing:

Math jokes collection by Andrej and Elena Cherkaev

mathematical jokes and mathematical folklore.
www.math.utah.edu
​
A biologist, a physicist and a mathematician were sitting in a street cafe watching the crowd. Across the street they saw a man and a woman entering a building. Ten minutes they reappeared together with a third person.​
- They have multiplied, said the biologist.​
- Oh no, an error in measurement, the physicist sighed.​
- If exactly one person enters the building now, it will be empty again, the mathematician concluded.​

So, @harpazo, was this question just a joke, or was it serious? Neither the question nor the answer can be judged accurately without knowing the context. I suspect it has nothing at all to do with Common Core.
 
Thank you everyone. Return to Sullivan this weekend. Moving today.
 
harpazo said:

Students & Word Problems

Replies: 16
able2know.org
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The person who posted that question for you stated that the constraint you have applied comes from your belief in how people work. I doubt anyone has seen a room containing a negative number of people, or a negative number of any physical objects.

Your statement that if four people are in a room, then at most, four people can leave, seems sound to me, and comports to the reality we can all observe. Sometimes people enjoy trolling others online.
 
Dr.Peterson said:
They have multiplied, said the biologist.

I personally side with the measurement error. Are you sure there were only four there?
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Ooh! Maybe we can get a vision thing going! There were actually 6 people entering but the observer could only see 4.

-Dan
 
MarkFL said:
The person who posted that question for you stated that the constraint you have applied comes from your belief in how people work. I doubt anyone has seen a room containing a negative number of people, or a negative number of any physical objects.

Your statement that if four people are in a room, then at most, four people can leave, seems sound to me, and comports to the reality we can all observe. Sometimes people enjoy trolling others online.
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We are totally on the same page.
 
harpazo said:
What is the purpose for asking such a question? It is not asking for the perimeter, area or how to manage money in life, you know, interest on bank loan, etc.
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The purpose of my question was to point out that YOU have unfounded aversion towards common-core.

The question you posed was posted in a thread that you started (https://able2know.org/topic/535766-1#post-6913631) and it had nothing to do with common-core.

Yet you quickly started the "fake news" about common core. Just like some politicians, you must believe that repeatative fake-news becomes real news.

Instead of blaming external environments that may have affected some lives, I look at the fun-centric attitude of the individual and ponder their direction of future-life.

The problem you posted (posed by someone else) did NOT state that there were ONLY four people in room. There could have been 167 people in the room - including the four people in question. Then of course six people can leave (which may or may not include any or all of those four aforementioned people).
 
Subhotosh Khan said:
The purpose of my question was to point out that YOU have unfounded aversion towards common-core.

The question you posed was posted in a thread that you started (https://able2know.org/topic/535766-1#post-6913631) and it had nothing to do with common-core.

Yet you quickly started the "fake news" about common core. Just like some politicians, you must believe that repeatative fake-news becomes real news.

Instead of blaming external environments that may have affected some lives, I look at the fun-centric attitude of the individual and ponder their direction of future-life.

The problem you posted (posed by someone else) did NOT state that there were ONLY four people in room. There could have been 167 people in the room - including the four people in question. Then of course six people can leave (which may or may not include any or all of those four aforementioned people).
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YOU are correct. Common Core is garbage.
 
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