profase

3b. You just had to optimize the volume, they gave you the rate. You just set 2000 - R(t) = 0.
I got sqrt(t) = 5, t = 25.

Then yeah, if you get part b, part c is easy. Just 60000 + fnInt(2000-R(t),x,0,25).

NeilGulati

the whole thing was easy. 1d use cylinders. u have height and radius. just 2(3.14)fnint ,(x)f(x),x,0,2 if i remember numbers right. for 3b you have the rate at which its entering and rate at which its leaving. because you have the RATE it implies it means it is the first derivative, so find the zeroes and use first derivative test to find maximum time. it is 25. for 3c you have the starting volume. and because until time 25 the amount entering exceeds the amount leaving, verified in part b, you will do 60,000 + (3.14)fnint, 2000-400(t)^.5, or something like that if i remember numbers right

Beef

I did it a different way. I found the average value of the depth (3 - x) of the pond, and took the area found in part a) and multiplied it by that average depth. I think it was a bit easier than setting up a nasty product integral (even though your calc can do it in a few sec).

By the way, how well do you have to do to get a 5? I nailed the free response (except for a section or two where I might have made some mistakes), and skipped 3 multiple choice. The rest of the MC I was pretty confident about.

seanbow

Beef: I don't think that method works, actually. That way you get 2 for an answer, but the other way you get 8.something.

newyorkjets

i hated the non - calculator MC part, thought it was hard.
loved Calcularot MC and FR parts, easy.
I hated the oil one in FR, have no idea how to figure it out.
lets hope i pass, i think i f-ed up on the calculations for ln and logs at FR in end.
i might have did this: integral of lnx= 1/x

Sandra33162

hey I'm just wondering if the starting point for a 5 in calculus is really 60-100+, and if so what would be the equivalent to getting a 60 (m/c and frq scores)?

Beef

No, it works, I remember getting 8 or 8.something . Volume of an extruded part is just area of the base times the height. If you find the average height of a solid with an irregular height and treat it like an extruded part, it still works (I consulted this with my physics teacher, who knows more calculus than all the calculus teachers in my school combined).

rappoltpierre

i did it the same way as Beef. It definitely works.

Sandra33162

does anyone know when the scoring guidelines for the FRQ will be posted on collegeboard?

Sandra33162

I would just review the FRQ with my teacher but I haven't been in class since a day before the exam, other AP test...

seanbow

Really? Hm. Weird. Oops, I definitely was doing it wrong before... but now I get 8 with half of the integral of 3-x times the integral of sin(pi x) - (x^3 - 4x), as opposed to 8.370 with the integral of (3-x) times (sin(pi x) - (x^3 - 4x)).

carsonne

we went over the FR in class... i made a bunch of dumb mistakes but hopefully i do well enough on the MC... :/

was hoping for a 5 but expecting a 4 and hopefully NOT a 3

Beef

I think I remember getting exactly 8 in that question