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Fun post! Wheels or Doors?

  • 1.  Fun post! Wheels or Doors?

    Posted 03-18-2022 14:25

    Just for fun on this Friday afternoon, I wanted to ask our members for their thoughts on the latest viral debate happening online – are there more wheels or doors in the world? There must be a mathematical approach to this question… So tell us, are you #TeamWheels or #TeamDoors, and why? 

    Everyone who responds to this thread by end of day Thursday, March 24th (ET) will be entered into a drawing to win a Starbucks gift card! If you have a photo on your profile, you get a bonus entry in the drawing. So make sure to post a photo if you haven't already!



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    Jill Capello
    Membership Associate
    INFORMS
    Catonsville MD
    jcapello@informs.org
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  • 2.  RE: Fun post! Wheels or Doors?

    Posted 03-22-2022 10:10
    Hi Jill,
    At first I was thinking there are more doors because buildings have many doors. Then I thought about an office building - there are probably more wheels in the parking garage than doors in the building. I'm going with #teamwheels.
    I'm interested to know what our members think. I know it isn't the TSP or knapsack problem but it is interesting.

    Elena ​​​

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    Elena Gerstmann
    Executive Director
    INFORMS
    egerstmann@informs.org
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    Original Message


  • 3.  RE: Fun post! Wheels or Doors?

    Posted 03-23-2022 02:55
    Edited by Ian Korpi 03-23-2022 02:56
    The mention of the vehicles in the parking garage got me thinking -- what constitutes a door, and what constitutes a wheel for this problem?

    Do we count only wheels that are on an axle and used in contact with the ground? What about the flywheels in these vehicles? Then we also have the 'wheels' of tracked vehicles to consider. What about wheels in storage?

    It's a similar issue with doors. Do we count only the doors of permanent, fixed structures? There are the doors on the vehicles as well. Are doors any kind of covering, like a curtain used to divide one room from another, or are they of a certain kind of material?

    This has been discussed elsewhere, with things like mailboxes and camera lenses possibly being considered 'doors', but in order to think about possible mathematical models, I think a consensus on these definitions is a good starting point.


    Original Message


  • 4.  RE: Fun post! Wheels or Doors?

    Posted 03-23-2022 11:10

    Ian, I echo your sentiments. As I was drafting my reply to this post, I found the definition of wheels and doors to be quite valid in the consideration.

    My initial thought process started with vehicles with which I attributed various ratios of doors to wheels. I would make a conjecture that the most common vehicle has 4 doors and 4 wheels (1:1). Then there are 2 door cars (1:2), motorcycles/bikes (0:2), and large trucks (1:6 --from 2 cab doors and a container door for 18 wheels). In this scenario, wheels seem to grossly outnumber doors. 

    When considering dwellings, however, I believe a conservative estimate is 1 door for every person. When considering commercial/non-residential buildings, there are likely a large number of extra doors added to this total. Safety requirements even advocate for extra doors! 

    I do think the biggest cause for the discrepancy is defining wheels. For example, if we can agree that doorknobs are wheels and axles...then I think undoubtedly there are more wheels in the world.



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    Jayna Glover
    Consulting Partner
    Roar Simultion
    Alpharetta GA
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    Original Message


  • 5.  RE: Fun post! Wheels or Doors?

    Posted 03-24-2022 13:52
    It certainly depends on the different types of doors and wheels that are considered. What if we include the doors of the vehicles? Given that there are about 1.4 billion cars alone worldwide. I am inclined toward #teamwheels. ​

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    Banafsheh Behzad
    Associate Professor
    College of Business
    California State University, Long Beach
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    Original Message


  • 6.  RE: Fun post! Wheels or Doors?

    Posted 03-24-2022 20:54

    The assumption here is that a wheel is a device helping a person to move from one place to another (no shopping carts for that matter), and a door is a device that helps one to enter or exit a building/room.

     

    My rough estimate is as follows.

     

    First of all, assuming that a spare tire is not a wheel, we can disregard all four-door sedans, because they have 4 wheels. 


    Second, let us take a look at larger vehicles such as 14-wheelers. I could not find the exact number existing in the world, but clearly, the total number of people on Earth is several orders of magnitude higher than the number of trucks, while the number of wheels in a truck exceeds the number of doors in a truck roughly by one order of magnitude. These trucks can also be disregarded as the number of wheels will not dominate significantly. The same goes for buses, for example, they in fact have fewer wheels than trucks. 


    Third, speaking of doors. About 2% of the world's population lives on the streets. This number is huge, but for the purposes of this post, 2% is a tiny bit less than 2 orders of magnitude less than the rest 98%. Therefore, the number of wheels used by homeless people is negligible (at most, they would use a bicycle – 2 wheels.)


    The rest of the population (98%) lives indoors and uses doors. There are 2 billion bicycles in the world (we are already done with cars/trucks), making it roughly 0.28 bicycles per person (or 0.56 bicycle wheels per person). The number of housing units in the world is 1.16 billion. At a bare minimum, there is 1 entrance door, making in at least 0.17 doors per person. This estimate can be improved by using the information we know: there are 139 million houses in the USA. Based on Tampa-based Masonite estimation, the average number of doors is 19. By using this additional information, the overall estimate of doors per person immediately jumps up to 0.68 per person (higher than 0.56 bicycle wheels per person). We have not yet counted the number of extra doors (in addition to the entrance doors) in the EU and other developed regions, but what we have gotten so far is sufficient to conclude that the number of doors is higher.

    Lastly, let us not forget that there are malls, skyscrapers, stores, hotels, etc. They all use doors and no wheels. So #TeamDoors.

    P.S. After writing the above, I decided to look at Google's verdict. According to Hank Green, "the wheels on his children's toy cars were functional, but the doors weren't." He sided with #TeamWheels 



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    Mikhail Bragin
    Assistant Research Professor
    University of Connecticut
    Storrs CT
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    Original Message


  • 7.  RE: Fun post! Wheels or Doors?

    Posted 03-25-2022 03:32
    I think your assumptions are overly restrictive. There's nothing in the definition of the word "door" that restricts it to "humans entering or exiting a room" and there's nothing about the definition of "wheel" that restricts it to moving humans.

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    Kenneth Schultz
    Unaffiliated
    Xenia OH
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    Original Message


  • 8.  RE: Fun post! Wheels or Doors?

    Posted 03-25-2022 03:22
    In my house, 131 doors to 54 wheels. 

    Most of the doors are on cabinets. I included the hatch on the SUV but not the hoods on the cars. But I probably should have included the hoods. 
    This doesn't include windows that open like doors but does include the sliding glass door.

    Most of the wheels are on chairs, but with a surprising amount on vacuum cleaners and lawn tools, there's 3 wheels and no door on the edger.
    This doesn't include gears, balls or ball bearings or things like that.

    There are a bunch of toys and Legos in the basement I didn't count, and a lot fewer doors, so make that 140 to 80 (we have a lot of Legos.)

    Go to an office building, definitely more doors than wheels as the cars outside have already been counted at home. A huge number of doors. But any retail with shopping carts and the wheels win hands down, same with toy stores. But enough to make up for all the cabinets in the world. I don't think so. 

    Doors.

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    Kenneth Schultz
    Unaffiliated
    Xenia OH
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    Original Message


  • 9.  RE: Fun post! Wheels or Doors?

    Posted 03-25-2022 03:37
    Then again, manufacturing has lot of wheels and not all that many doors. Lots and lots of carts and parts moving equipment.

    Do the wheels on the conveyor belt count?

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    Kenneth Schultz
    Unaffiliated
    Xenia OH
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    Original Message


  • 10.  RE: Fun post! Wheels or Doors?

    Posted 03-25-2022 05:08
    Excellent point:
          Do the wheels on the conveyor belt count?
    Never thought about it, but conveyor belts are the real killer. Can't imagine how many wheels even a small airport baggage handling system does have? Can't think of any toy or small tool that has doors. Their moving parts are called different names. Therefore, thanks to Kenneth, I am changing my vote to #teamwheels.

    TGIF again,
    yavuz

    P.S. Hope to say one day TGWIO. Peace for Ukraine...
    ​

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    Yavuz Gunalay
    Professor
    Bahcesehir University
    Istanbul
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    Original Message


  • 11.  RE: Fun post! Wheels or Doors?

    Posted 03-25-2022 11:49
    Love this topic and the discussions! 

    I was on #TeamWheels because I counted the wheels on the office moving cabinets and some of the tools. My thought was it's obvious that each room has one or two door but probably have multiple wheels. Same for the cars.
    But reading the dicussions made me realize that I forgot about car doors! And cabinet doors if they count.

    Now I don't know anymore. I think it'll take sometime for me to find some data to be able to get closer to the result of the question.​

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    Xiaonan Shang
    Data Analyst
    University of Tulsa
    Jenks OK
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    Original Message


  • 12.  RE: Fun post! Wheels or Doors?

    Posted 03-25-2022 12:04
    I had a thought while trying to get to sleep last night, what about wheels and doors in landfills.  I think the majority of doors are cabinets, vehicles, and houses. When they are done with their useful life they are most likely to get either recycled or destroyed. Most wheels are on toys. They get thrown in the landfill, mostly intact.

    I'm going to have to be a flip-flopper and go with Wheels.

    As for an analytical approach - I have no idea why it would ever be worth the effort but the best method I can think of is to get an estimate not by estimating current inventory but rather by estimating annual production.

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    Kenneth Schultz
    Unaffiliated
    Xenia OH
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    Original Message


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