07Q-59

[mathcoach]

I am a new math coach and inherited a bunch of past materials. I have been using the TMSCA High School Calculator test #8 from Jan. 27, 2007 (because there was a worked out key!) and am having trouble understanding the set up of question #59.

My integral is: a^2*pi Int 1 to 9 (1/x^2) dx = 185.

Evaluating: a^2* pi [8/9] = 185

a = 25.6

The key shows:

Integral: 2 * pi * a Int 1 to 9 1 dx = 185

Evaluating: 2* pi * a x = 185 from 1 to 9

a = 3.68

Could you help me?

Thanks.

[louie]

well using calc, using the disc method

pi * (int (R^2-r^2)dx) from 2.5 to pi.....

R being the big radius and r the little radius

R= (top-bottom function) (5(e^(-.4x))*sin(5x))-(-1)
r=(top-bottom function) (0)-(-1)

anyone got an easier way of explaining it?

just plug in R and r into (pi * (int (R^2-r^2)dx) from 2.5 to pi)
that equals 6.64

[mathcoach]

I guess I was unclear in my previous post. What I don't understand is the worked out solution for that particular problem given with the test. The setup
doesn't make sense to me. I showed it to another calculus teacher, and they got the same answer that I did, which was different than the test solution. Maybe I will scan the worked-out solution and email it along with my question to the webmaster.

Thanks!

[The3point14]

I do not have this test to look at the question and analyze it, but from my experience, TMSCA has had a few mistakes including wrong answers, solutions, and typos on Calculator, as well as Number Sense and Math tests. These things happen, so I wouldn't doubt that the key/solution could be incorrect.

EDIT: I'm not saying that TMSCA is not a quality test, because it definitely is the best after UIL Releases, IMHO.

[AuSmith]

It would be nice to have some more editing before the tests are given at competition, though. It's the most frustrating thing to see

(rad) sin(55 degrees)

and be expected to write the sin of 55 radians.