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I always start the semester with this article, Why American Consumers Can’t Add:

American Innumeracy


It was written in 2009 right after the financial collapse, but it is still very relevant with nice statistics that set the stage for developing the fundamental skill set for quantitative literacy.  The reasons for the subprime housing bubble quickly take us to the National Assessment of Adult Literacy (NAAL) and the fact that Americans are much worse at math than most of us would think.  The NAAL is where I get the statistic that 87% of adults are quantitatively illiterate in this country, with only 20% being able to reliably calculate mortgage interest and 20% being unable to calculate weekly pay from an hourly rate.  Over half the adults in the U.S. cannot

  • compute the total order from a sales catalog
  • determine if they have enough gas to reach the nearest gas station
  • calculate the cost of a child as a % of their budget

NAAL results

The author of the article, Bob Sullivan, closes with a stark admonition about the “hidden epidemic of innumeracy” that will doom us to repeat our fiscal mistakes.  The good news is that our QR courses are taking up the challenge and addressing this quantitative illiteracy head on!

On the take home quiz I ask the following questions:

  1. a)   You and a friend go down to The Gelato Fiasco and order two items: one costs $4.50 and the other $3.75.  What would be a 15% tip for the combined total?
    b)   20% tip is how much more than a 15% tip? Hint: This one is tricky (which isn’t much of a hint but you get the idea).

    1. 5% more
    2. 10% more
    3. 25% more
    4. 33% more
  1. If a person borrows $450 at the beginning of the month and promises to pay back $543.75 on payday at the end of the month, what is their monthly interest rate? What is the associated APR of this payday loan?
  1. Compute the amount of money US adults spend each year on getting tax preparation help for the 1040 EZ form (the information you need is in the article!).
  1. Joel Best’s nomination for the “worst statistic ever” is a mutation of the original “The number of American children killed each year by guns has doubled since 1950.” Reword this sentence so that it means if the number killed in 1950 was 1 then in 1951 the number killed would be 2 then the next year 4 then 8 etc.
  1. Does the doubling of childhood gunshot deaths from 1950 to 1994 mean our society has become more violent? Explain!




4 thoughts on “Innumeracy

  1. 1B has to be 5% correct? it says it’s tricky so I assume it is not but no matter what I do I still come up with 5%


    Posted by Ashley | September 29, 2015, 8:33 pm
    • It is the same thing as the percent difference between $20 and $15. $20 is $5 more than $15 (total difference) but is $20 only 5% more than $15? Of course, we need a good understanding of what it means to say something is “5% more than”. As a hint: $22 is 10% more than $20.


      Posted by egaze | September 29, 2015, 8:56 pm
  2. A report of what happened when I used this for the first time…

    After the first day of classes, which was filled mostly with introductions, syllabus, and conversation about the philosophy of the course, I assigned that they read this Numeracy Article, together with the first three questions posted. I asked my students to take some notes, to write down their thoughts/responses to the questions, and not just a numerical answer.
    In the past, I had talked (myself) about the poor state of QR in the country – and they always tended to take this a bit personal, which back-fired with somewhat negative attitudes rather than motivation to get better.
    Having them read this nice little article was a much better idea. A number of students volunteered to report their thoughts about the article after I prompted and prodded a little. Students expressed that they were surprised and unaware! One student actually picked up on the point that while US students performed near the bottom, they thought they performed at the top! This really worked SO MUCH BETTER!

    I am so excited, that I want to say more: In the next (only the second!) class, I gave each student a sheet with the three questions, and assured them that this will not be graded, not even any judgement on their performance, but that this exercise is for me and for them to learn a process I hope to use often. The first round, I asked students to refrain from talking to their neighbors, and to consult their HW notes, if they had any, and to leave blank parts they could not respond to in the five (or so) minutes I allowed. I urged them to write enough so that a reader can see how they arrived at their answer. I collected the papers (with names, which was not really necessary), and gave each pair another blank copy with the same questions and instructions. I allowed more time for this second round of pairs working on the questions, and I encouraged pairs (after a while) to talk to the pair sitting across from them… I walked around, listening in and helping a bit, explaining what I meant by writing enough to show what you thought (e.g. 20 million x $100 is enough to explain the answer for Question 3). Also, I pointed out, loudly, whenever I heard someone ask a question of their peers (like: “Why did you divide this by that”) that this is an excellent question to ask when working in a team…

    The result was amazing and impressive. The students worked together beautifully! And I had wracked my brain over how to get them to work together better!

    When we discussed the questions, and showed different ways of answering them (which was natural at this point, and there were always at least two, and in one case even three totally different approaches to calculating the tip!)

    We ended up getting to talk about large numbers, “packets of 3 zeros” and thousand, million, billion etc, multiplying or dividing by 10, and which way the decimal point moves as well as how one can easily decide which way it must go, how to roughly calculate 15% of something, and they saw the power of visualizing things, when I tried to convince the students that 20% is 33.3% more than 15%…

    It was a beautiful start of the semester, and there are so many follow-up possibilities. I am excited about my decision to use some of these articles this time around. In the last few semesters, I felt I had no time to do it, and I did not have the time to read them all and find ways to incorporate them. I want to incorporate them at places where I think they fit.

    If anyone reads this, please leave a comment. This will encourage me to write brief reports of my experience for the other articles from this wonderful collection at this blog I will use as the semester goes on.


    Bernd Rossa, Xavier University, Cincinnati Ohio


    Posted by Bernd Rossa | January 12, 2018, 8:48 pm

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