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# Sal interviews the AP Calculus Lead at College Board

Video transskription

- So this is Sal Khan,
founder of the Khan Academy. And this is a very exciting
Skype call that we're on. I'm with Ben Hedrick, who's the lead for AP Calculus. What do you at the College Board? - Really, anything with AP
Calculus and AP Statistics is something that I have a
little bit of control over. So for example, for AP Calculus, anything with the curriculum,
anything with the assessment is something that I work with. - And I'm sure that you're as excited as I am and, you know, several hundred thousands of
students are around the country for the AP exams that are coming up in roughly a little less than a week. And I thought a fun
place to start would be when you guys write the test, what are you trying to assess? What's the spirit of the questions? Both on the multiple choice
and the free response section. - So what we're looking for from students is evidence of good, conceptual
understanding in calculus. Now, we have some things that
are gonna test procedures, but really, we want students
to understand what's going on with the calculus rather
than just calculating things or putting numbers on paper. A lot of thinking
questions, a lot of insight to make sure that whatever
good calculus those students have learned in their courses, we're assessing it on the AP exam. - And I've done a bunch of
example problems for the AP exam, and yeah, my sense of it is you sometimes will do
some of the minutiae work or you'll give the formula, and you're really trying to understand whether students understand the essence of what an integral is, or the essence of derivative
as a rate of change, or the slope of a tangent line. So, if you were preparing for this exam, if you were the students, what you suggest to them? You know, obviously we have
a little less than a week for this current test, so what advice would you
have for those students? And then just generally, as
students go through the year, how should they think about it? - Yeah, the advice I would give is dependent on how much
time the students have to prepare, so the advice that I give at the beginning of the year
is different from the advice that I give now, several
days before the exam. Getting ready for it, first, relax. You know, this is a calculus exam. We're not gonna be throwing
anything at you from left field. It's calculus. You need to know limits. You need to know derivatives. You need to know integrals. In terms of preparation, make
sure you're taking the time to review the basics. Every question that they see is gonna hit one of those big topics, so make sure you know
your derivative rules, make sure you know your integral rules. Take a look at the old exams and see how we're asking questions. And you'll at the patterns and
see that we're always asking about understanding
what a derivative means, understanding integration
or the idea of accumulation. There are no secrets on the exams, so really stick with what we've done. Make sure that you're thinking of ways to apply to your good knowledge, and just review your basics. - And my experience with the
exam is there's a lot of, as you just said, really the
mainstream, meaty topics. You know, chain rule, fundamental theorem, or theorems of calculus, things like that. What's your sense of the more, what I would concern maybe a
little bit more, the minutiae, some of the more special case derivatives, or special case integrals,
you know, arc tangent and, how much does that play into the exam? - You know, I think, Sal,
you've actually answered your own question in asking that, is it is the minutiae. So really, at this point in
time, if you're getting ready for the exam, spending time on minutiae is not where you're gonna be
best served with your time. You should be hitting the major things, and you said it right at
the beginning, chain rule. I mean, any kind of question
we do with derivatives, you know, if you're doing maxes or mins, if you're doing tangent lines, if you're doing a related rates problem, they're all derivatives,
derivatives, derivatives. And if you're having
trouble with chain rule, it doesn't matter how much
minutiae you spend time with, the chain rule's gonna come up. So I would say don't sweat the minutiae. There might be something on the exam that you haven't reviewed
as much as you want to, but it's gonna be one
single, solitary question. Basic derivatives are going to form, well, the basis for all those problems. So that's where your time is best spent. - Yeah, I definitely get that sense. Especially, you know, how
do you interpret the first, second, you know, derivatives, concavity. Things like that, those
seem to show up a lot. But once again, that's a
conceptual idea of derivatives. And on the integration side, I've been doing a bunch
of the free response. It just seems like, I mean, you know, what happens if you swap
the bounds of integration, or if you add integrals. So a lot of the properties and
the conceptual understanding of what an integral is, but not necessarily the fancy tricks. At least at this point,
if you're studying. - Absolutely, there's
nothing that we go after the fancy tricks. We're not trying to ask trick questions or play any gotcha moments on it. It's really assessment of calculus. And for the students who
have been going through these great courses all year, this is a wonderful opportunity to show us everything that you know and get a really great score on the exam. - And what about calculator? I mean, I was doing some
of the free response. That first part of the free response, knowing your calculator well helps. - Oh, absolutely. The calculator's a tool, and like any tool, you want to make sure that you're applying it
appropriately and strategically, which sometimes means
using your calculator, and using it well and correctly, but other times not using your calculator. I mean, even on the free response section where the calculator is being used, we expect students to show their work. If you're taking an integral, we wanna see that you've
actually taken that integral. Now, the calculator
will do the work of it, but we wanna see the notation that says this is the integral you calculated, and this is the answer you obtained. And then do whatever you
will with that answer as required by the question, but good communication through writing, even on the calculator
section, is necessary. - And for students taking the BC exam, above and beyond the core differentiation, integration, you know,
a lot of what you learn about parametric equations
is actually just an extension of what you learn in
differentiation, integration. But probably some of the convergence tests are something to become
pretty familiar with. - That would be correct, yes. - And in terms of grading of the exam, you know, some people, to get a five or a high, my understanding is you
don't need to answer absolutely every question perfectly. - Well, like any test,
if you want to do well, you don't have to have perfection on it, and this is a test where
students are coming in and it's a three hour timed test, well, a little over three hour timed test, and you know, you can do
a lot of really good work and earn a five pretty easily. So I wouldn't tell anyone
to go in there worrying about trying to figure out
what magical numbers they need to get in order to get a
perfect score on the test or to get a five on the test or whatever it is that they're going for. Just go in like you would on any test, do your best on every question, get every point that you can, and hopefully it'll work out fine for you. - What advice would you have for students, especially on the free response where there's multiple sections, and if, you know, on part A they say, what, that, that's, I don't get what that, what, you know, should they
skip to the next free, what should they do? - I actually have very
common advice on that one and that's to make sure
that students are trying every part of a free response question. One of the misconceptions students have is exactly what you said. If you hit part A and you're
freaking out a little bit because you don't know
what part A is about, that's okay, move on to part B. There are some questions
where the answer for part b depends on part A, but for
the majority of the questions, they're separate pieces. So part A, part B, part C, if there's a part D, they might all be asking
very different things. And if you have trouble even with part C, that doesn't mean the question gets progressively more difficult. Give part D a try. And a lot of the things
that we do give points for are good, solid calculus work. So if you can set up a problem, maybe you don't have time to finish it, maybe you make some
mistakes along the way, the answer point is only one little point out of the nine. There are other points for the setup and the conceptual
understanding of the problem, and a lot of students have
good conceptual understanding that they could set up, pick up a point here,
pick up a point there, but they panic a little bit, and they move on to another question and never come back. And that's okay if you want to
move on to another question, but absolutely I would say, if you're having trouble with part A, that's all right, take a look at part B. - And one thing that I've observed is a lot of these questions, at
first when you look at 'em, like oh wow, this looks like some really, you know, super deep thing, but it really is some
core basic calculus ideas, and that if you're on the right track, it's actually quite simple. Would you say it's fair
if a student finds himself doing a very hairy calculation that they might question
whether they need to? - I would go beyond might. They should question what they're doing. If you've done something
where you feel like you need to prove a new calculus theorem in order to answer it, something has gone
terribly, terribly wrong. And also, if you feel like you need to bring in some sort of mathematics you've never seen before in calculus, as much as I hate to say it,
you know, this is calculus. It's limits, it's
derivatives, it's integrals. Even though there's a lot
of wealth in that one, if you're doing something beyond that, probably something has gone wrong. - Yeah, yeah. Well, thanks. I think, you know, thousands of AP students are
gonna really appreciate that. Any other parting words
for the coming test? - You know, it's the same thing that I used to tell my students when I was teaching AP Calculus, this is just another test, and the beauty of AP is
the teachers have been prepping their students since
the beginning of the year. It's one of the few tests where everyone knows what's coming, so when you sit down and you've
got free response questions, you've got multiple choice questions, you know, there really
shouldn't be any surprises. This is the stuff they've seen all year. They know what to do. Take a moment, take a breath, take a look at the problem, get all the points that you can. Show us that good calculus. - Awesome, and I'll throw in a plug. We have tons of resources
for the students as well, and we're gonna have our
office hours on Monday. So, super exciting. Thanks a bunch, Ben. - No, thanks for having me.