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Chicago Prison Escape

by Robert Kaplinsky


Act One

  • Robert Kaplinsky

    Robert Kaplinsky

    December 19, 2012

    How many bed sheets would the prisoners need to escape?

  • 1.

    What is a guess that is too low?

  • 2.

    What is a guess that is too high?

  • 3.

    What is your best guess?

  • 4.

    What factors may affect the accuracy of our answer?

Act Two

  • ImageFull view of the prison building (escape was on the other side of the prison)
  • ImageView of the rope coming out of the cell
  • ImageDetailed view of how the sheets were weaved to make the rope
  • ImageView of the rope as it approached the street.
  • Image“Roof of a corridor that connects to an adjoining parking garage”
  • Teacher note
    There are many assumptions that need to be made to solve this problem. Here are some to consider:
    Distance from the prisoners’ cell to the ground – The cell is on the 17th floor and the video states that the rope “extends down about 15 stories and ends just a few feet shy of the roof of a corridor that connects to an adjoining parking garage.” The corridor appears to be about two stories tall, which matches 15 stories (17 stories – 2 stories). Assuming prisons are like most buildings and that each story is approximately 10 feet high, then their rope descended about 150 feet.
    Length of a bed sheet – I am assuming that each sheet is approximately 6 feet long.
    Based on those assumptions, I would expect students’ first calculations to be something like (170 feet – 20 feet) / 6 feet per sheet which gives an estimate of about 25 sheets.
    Unsurprisingly, the exact number of sheets used has not been released by the prison. The best data I have comes from the article included in the “Download files” link that cites “about 200 feet of bed sheets”. It isn’t clear how the report came up with that estimate, so it is worth considering that your students may have come up with a more realistic estimate. Points to discuss to help students reflect on assumptions they may have incorrectly made include:
    Dividing by 6 implies that the sheets are lined up end to end. Since they are obviously being tied together, the knots will use up some of the length.
    Standard twin bed sheets are actually 75″ long. Long twin bed sheets are actually 80″ long.
    Each floor may be taller than 10 feet (especially the first floor and ninth floors).
    The prisoners may have made the rope more than one sheet thick. Visually the rope appears to be braided from strips of sheets rather than leaving the sheets intact. It looks like the sheets are at least two sheets thick.
    A new calculation based on these assumptions is: (170 feet long x 2 sheets thick) / 5 feet of usable fabric per sheet is 68 sheets.
    One other interesting factoid about this escape is that, according to Wikipedia, “each cell has a slit window which is 5 inches wide by 7 feet long.” I do not know how someone was able to escape out of a window that narrow.
    Lastly, thank you to Andrew Stadel for the suggestion to leave out the part of the video that states the prisoners escaped. As he mentioned, “students will be drawn to that question which allows you to discuss the details.” So, when the time is right you can share with students that both prisoners did escape.


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