MoP 2 : A One-Way Conversation

We’re not particularly looking to blog about censorship. In general, we think the problem (in, e.g., Australia and the US) is overhyped. The much greater problem is self-censorship, where the media and the society at large can’t think or write about what they fail to see; so, for example, a major country can have a military coup, but no one seems to notice. Sometimes, however, the issue is close enough to home and the censorship is sufficiently blatant, that it seems worth noting.

Greg Ashman, who we had cause to mention recently, has been censored in a needless and heavy-handed manner by Sasha Petrova, the education editor of The Conversation. The details are discussed by Ashman here, but it is easy to give the story in brief.

Kate Noble of the Mitchell Institute wrote an article for The Conversation, titled Children learn through play – it shouldn’t stop at pre-school. As the title suggests, Noble was arguing for more play-based learning in the early years of primary school. Ashman then added a (polite and referenced and carefully worded) comment, noting Noble’s failure to distinguish between knowledge that is more susceptible or less susceptible to play-based learning, and directly querying one of Noble’s examples, the possible learning benefits (or lack thereof) of playing with water. Ashman’s comment, along with the replies to his comment, was then deleted. When Ashman emailed Petrova, querying this, Petrova replied:

“Sure. I deleted [Ashman’s comment] as it is off topic. The article doesn’t call for less explicit instruction, nor is there any mention of it. It calls for more integration of play-based learning in early years of school to ease the transition to formal instruction – not that formal instruction (and even here it doesn’t specify that formal means “explicit”) must be abolished.”

Subsequently, it appears that Petrova has also deleted the puzzled commentary on the original deletion. And, who knows what else she has deleted? Such is the nature of censorship.

In general we have a lot of sympathy for editors, such as Petrova, of public fora. It is very easy to err one way or the other, and then to be hammered by Team A or Team B.  Indeed, and somewhat ironically, Ashman had a post just a week ago that was in part critical of The Conversation’s new policy towards climate denialist loons; in that instance we thought Ashman was being a little tendentious and our sympathies were much more with The Conversation’s editors.

But, here, Petrova has unquestionably screwed up. Ashman was adding important, directly relevant and explicitly linked qualification to Noble’s article, and in a properly thoughtful and collegial manner. Ashman wasn’t grandstanding, he was contributing in good faith. He was conversing.  Moreover, Petrova’s stated reason for censoring Ashman is premised on a ludicrously narrow definition of “topic”, which even on its own terms fails here, and in any case has no place in academic discourse or public discourse.

Petrova, and The Conversation, owes Ashman an apology.

Implicit Suggestions

One of the unexpected and rewarding aspects of having started this blog is being contacted out of the blue by students. This included an extended correspondence with one particular VCE student, whom we have never met and of whom we know very little, other than that this year they undertook UMEP mathematics (Melbourne University extension). The student emailed again recently, about the final question on this year’s (calculator-free) Specialist Mathematics Exam 1 (not online). Though perhaps not (but also perhaps yes) a WitCH, the exam question (below), and the student’s comments (belower), seemed worth sharing.

Hi Marty,

Have a peek at Question 10 of Specialist 2019 Exam 1 when you get a chance. It was a 5 mark question, only roughly 2 of which actually assessed relevant Specialist knowledge – the rest was mechanical manipulation of ugly fractions and surds. Whilst I happened to get the right answer, I know of talented others who didn’t.

I saw a comment you made on the blog regarding timing sometime recently, and I couldn’t agree more. I made more stupid mistakes than I would’ve liked on the Specialist exam 2, being under pressure to race against the clock. It seems honestly pathetic to me that VCAA can only seem to differentiate students by time. (Especially when giving 2 1/2 hours for science subjects, with no reason why they can’t do the same for Maths.) It truly seems a pathetic way to assess or distinguish between proper mathematical talent and button-pushing speed writing.

I definitely appreciate the UMEP exams. We have 3 hrs and no CAS! That, coupled with the assignments that expect justification and insight, certainly makes me appreciate maths significantly more than from VCE. My only regret on that note was that I couldn’t do two UMEP subjects 🙂

UPDATE (22/4) The examination report has appeared.


WitCH 31: Decomposing

We have a short Specialist post coming, and we’ll have more to write on the 2019 VCE exams once they’re online. But, for now, one more Mathematical Methods WitCH, from the 2019 (calculator-free) Exam 1:

Update (04/07/20)

The main crap here, of course, is part (f): as commenter John Friend puts it, what the hell is this question supposed to be testing? And, sure, the last part of the last question on an exam is allowed to be a little special, but one measly mark? Compared to the triviality of the rest of the question?

Of course, students bombed part (f). The examination report indicates that 19% of student correctly answered that there is one solution to the equation; as suggested by commenter Red Five, it’s also a pretty safe bet that the majority of students who got there did so with a Hail Mary guess. (It should be added, the students didn’t do swimmingly well on the rest of Question 9, the CAS-lobotomising having working its usual magic.)

OK, so what did examiners expect for that one measly mark? We’ll get to a reasonable solution below, but let’s first consider some unreasonable solutions.

Here is the examination report’s entire commentary on Part (f):

g(f(x) + f(g(x)) = 0 has exactly one solution.

This question was not well done. Few students attempted to draw a rough sketch of each equation and use addition of ordinates.

Gee, thanks. Drawing a “rough sketch” of either of these compositions is anything but trivial. For one measly mark. We’ll look at sketching aspects of these graphs below, but let’s get on with another unreasonable solution.

Given the weirdness of part (f), a student might hope that parts (a)-(e) provide some guidance. Let’s see.

Part (b) (for which the examination report contains an error), gets us to conclude that the composition

\boldsymbol{g(f(x)) = e^{\left(3+2x-x^2\right)}} has negative derivative when x > 1.

Part (c) leads us to the composition

\boldsymbol{f(g(x)) = \left(3 - e^x\right) \left(1 + e^x\right)}

having x-intercept when x = log(3).

Finally, Part (e) gives us that the composition f(g(x)) has the sole stationary point (0,4). How does this information help us with Part (f)? Bugger all.

So, what if we include the natural implications of our previous work? That gives us something like the following: Well, um, great. We’re left still hunting for that one measly mark.

OK, the other parts of the question are of little help, and the examiners are of no help, so what do else do we need? There are two further pieces of information we require (plus the Intermediate Value Theorem). First, note that

\boldsymbol{g(f(x)) = e^{\mbox{\bf THING}} > 0}.

Secondly, note that

\boldsymbol{f(g(x)) = \left(3 + e^x\right) \left(1 - e^x\right)} = -}\mbox{\bf HUGE} if x is huge.

Then, given we know the slopes of the compositions, we can finally complete our rough sketches: Now, let’s write S(x) for our sum function g(f(x)) + f(g(x)). We know S(x) > 0 unless one of our compositions is negative. So, the only place we could get S = 0 is if x > log(3). But S(log(3)) > 0, and eventually S is hugely negative. That means S must cross the x-axis (by IVT). But, since S is decreasing for x > 1, S can only cross the axis once, and S = 0 must have exactly one solution. 

We’ve finally earned our one measly mark. Yay?

See the Evil Mathologer and the Evil Marty, December 3

On Tuesday December 3, the Australian Mathematics Society will hold a free education afternoon at Monash University, Clayton, as part of their annual conference. The talk details are below, and full details are here (and the lecture theatre details are below). You aren’t required to register, but you can do so here (and it is appreciated if you do).

UPDATE The talks will take place in Lecture theatre G81 of the Learning & Teaching Building (the bus stop side of Clayton campus). There’s a map of Clayton campus here.


1:30 Joanna Sikora: Advancing Women in Australian Mathematics: context, challenges and achievements

This talk reviews recent research undertaken by social scientists on women in mathematics. First, adopting a life-course perspective it summarises findings on the persisting gap in vocational interest in mathematics among adolescent boys and girls, including its potential to widen over time. Systematic differences between boys and girls in the choice of basic and advanced mathematics for ATAR (Australian Tertiary Admissions Rank) are discussed. Next, the consequences of these choices for tertiary education specialisations and availability of suitably qualified male and female graduates are considered.

Following this introduction, the talk summarizes research on underrepresentation of women in mathematics departments in Australia and across the world. The focus is on structural and institutional process which, over the course of individual careers, can amount to significant disadvantage even in the absence of overt discrimination. Topics discussed include cultural stereotypes that link perceptions of brilliance and academic talent with masculinity, gender differences in professional capital, i.e. peer esteem, accorded to male and female mathematicians, the gender gap in rates of publications and impact, documented bias in student evaluations and factors that enable success in establishing international collaborations. The talk concludes by summarizing the literature on practical steps that we can take to improve gender equity.

2:20 Julia Collins and Katherine Seaton: Knitting and Folding Mathematics

Mathematical thinking is not confined to mathematicians, but one place you may not expect to find it is in the world of crafts. Even the most maths-anxious knitters will display an astonishing familiarity with concepts from geometry, topology, number theory and coding, while modern origami artists are turning to mathematical algorithms to create models previously thought to be unfoldable. This talk will highlight a number of surprising connections between maths and craft, and will be followed by a hands-on session facilitated by Maths Craft Australia where people can create some mathematical craft for themselves. (Knitting/crochet needles and origami paper will be provided, but participants are also encouraged to bring their own! Knitting in the audience is strictly encouraged.)

2:45 Afternoon Tea

3:10 Marty Ross: How I teach, why the Mathologer is evil, and other indiscrete thoughts

In this shamelessly narcissistic talk I will reveal the One True Secret to teaching mathematics. Along the way I will explain why you can and should ignore STEM, calculators, Mathematica, iPads, the evil Mathologer, constructivism, growth mindset, SOLO, Bloom, flipping classrooms, centering children, lesson plans, skeleton notes, professional standards and professional development and many other modern absurdities.

3:35 David Treeby: How to Instil Mathematical Culture in Secondary Education

Over the past few decades, mathematicians have ceded the educational space to two groups: mathematics educators and technology companies. This has had a dire effect on what mathematics is taught and how it is taught. The result is a commodified brand of distorted mathematics. This talk will focus on how some well-resourced schools have resisted these changes, and how broad and equitable change will require the support of working mathematicians and their professional bodies.

4:00 Burkard Polster: Mathologer: explaining tricky maths on YouTube

In this session I’ll talk about my experience running the YouTube channel Mathologer and I’ll give you a sneak peek of the video that I am currently working on.

WitCH 29: Bad Roots

This one is double-barrelled. A strange multiple choice question appeared in the 2019 NHT Mathematical Methods Exam 2 (CAS). We had thought to let it pass, but a similar question appeared in last week’s Methods exam (no link yet, but the Study Design is here). So, here we go. First, the NHT question: The examination report indicates the correct answer, C, and provides a suggested solution:

\Large\color{blue} \boldsymbol{ g(x)=f^{-1}(x)=\frac{x^{\frac15}-b}{a},\ g'(x) = \frac{x^{-\frac45}}{5a},\ g'(1) = \frac1{5a}}

And, here’s last week’s question (with no examination report yet available):

Update (19/06/20)

As commenters have noted, it is very difficult to understand any purpose to these questions. They obviously suggest the inverse function theorem, testing the knowledge of and application of the formula g'(d) = 1/f'(c), where f(c) =d. The trouble is, the inverse function theorem is not part of the curriculum, appearing only implicitly as a dodgy version of the chain rule, and is typically only applied in Leibniz form.

As indicated by the solution in the first examination report, the intent seems to have been for students to have explicitly computed the inverses, although probably with their idiot machines. (The second examination report has now appeared, but is silent on the intended method.) Moreover, as JF noted below, the algebra in the first question makes the IFT approach somewhat fiddly. But, what is the point of pushing a method that is generally cumbersome, and often impossible, to apply?

To add to the nonsense, below is a sample solution for the first question, provided by VCAA to students undertaking the Mathematica version of Methods. So, the VCAA has suggested two approaches, one which is generally ridiculous and another which is outside the curriculum. That makes it all as clear as dumb mud.

WitCH 28: Tone Deaf

We haven’t yet had a chance to go through the 2019 VCE exams, but this question was flagged to me independently by two colleagues: let’s call them Dr. Death and Simon the Likeable. It’s from Mathematical Methods Exam 2 (CAS). (No link yet.)

UPDATE (05/07/20)

Even ignoring the stuff-ups, this question is ugly and pointless; the pseudo-applied framing is ugly and pointless; the CASification is ugly and pointless; the back-to-front integral is ugly and pointless; the matrix equation is ugly and pointless; the transformation is really ugly and really pointless. Part (f) is the pinnacle of ugliness and pointlessness, but the entire question is swill, from beginning to end.

And then there’s Part (e). “This question was not answered well” the examiners solemnly intone. Gee, really? Do you think your question being completely stuffed might have had something to do with it? Do you think maybe having a transformation of x when there’s not an x in sight may have been just a tad confusing? Do you think that the transformation then resulting in a function of t was maybe not the smartest move? Do you think writing an integral backwards was perhaps just a little too cute? Do you think possibly referring to the area of, rather than to the value of, an integral was slightly clunky? And, most importantly, do you think perhaps asking a question for which there is an infinite and impenetrable jungle of answers may have been an exercise in canyon-sized incompetence?

But, sure, those troublesome students didn’t answer your question well.

Part (e) was intended to have students find a transformation of the function f that effectively switches the behaviour on the intervals [0,4] and [4,6] to the intervals [2,6] and [0,2].  Ignoring the fact that the intended question was asked in an absurdly opaque manner, and ignoring the fact that no motivation for the intended question was either provided or is imaginable, the question asked was entirely different, and was ridiculous.

Writing the transformation out,

    \[\boldsymbol{\left\{\aligned &X = ax + c \\ &Y = by + d, \right.\endaligned}\]

we then have

    \[\boldsymbol{\left\{\aligned &x = \frac{X - c}{a} \\ & y = \frac{Y - d}{b}. \right.\endaligned}\]

So, the function y = f(t) y = f(x) can be written

    \[\boldsymbol{\dfrac{Y - d}{b} = f\!\left(\dfrac{X - c}{a}\right).}\]

Solving for Y, that means our transformed function Y = g(X) can be written

    \[\boldsymbol{g(X) = b\, f\!\left(\dfrac{X - c}{a}\right) + d.}\]

Well, this is our function g unless a = 0, in which case g doesn’t exist. Whatever. Back to the swill.

Using the result from Part (d), we have Part (e) asking for a, b, c and d such that

    \[\boldsymbol{\int\limits_2^0 + \int\limits_2^6 \ \left[ b\, f\! \left(\dfrac{X - c}{a}\right) + d\right]  \, {\rm d}X \ = \ \dfrac{15}{\pi}.}\]

What then are the solutions to this equation? The examination report lists a couple of families and then blithely remarks “There are other solutions”. Really? Then why didn’t you list them, you clowns? 

We’ll tell you why. Because the complete solution to this monster is a God Almighty multi-infinite mess. As a starting idea, pick any three of the variables, say a and b and c, to be whatever you want, and then try to adjust the fourth variable, d, to solve the equation. We’ll offer a prize for anyone who can give a complete solution. 

This question is as good an example as there can be of the pointlessness, the ugliness and the monumental klutziness of VCAA’s swamp mathematics.