SAT Reasoning Math with the TI-89

[iibogo]

Few questions...

1. I can't do inequalities with the regular TI-89...but the titanium can. Is it possible to transfer the titanium os to the 89?

2. http://img.photobucket.com/albums/v407/ammad/sat1.jpg

This is an SAT question. To answer this question I thought I could just solve the system of equations (a^(1/2)b^(1/2))^6 = 432 and a x b = z for z. But that doesn't work on my 89..(anyone with a titanium, try this out?)

I also wanted to try an solve for A x B straight up but the 89 says I can only solve for one variable. Any suggestions?

3. http://img.photobucket.com/albums/v407/ammad/sat2.jpg

This goes back to the inequalities, can the 89 titanium do this?

Thanks.

 

[iibogo]

TI 89 + SAT Math

Few questions...

1. I can't do inequalities with the regular TI-89...but the titanium can. Is it possible to transfer the titanium os to the 89?

2. http://img.photobucket.com/albums/v407/ammad/sat1.jpg

This is an SAT question. To answer this question I thought I could just solve the system of equations (a^(1/2)b^(1/3))^6 = 432 and a x b = z for z. But that doesn't work on my 89..(anyone with a titanium, try this out?)

I also wanted to try an solve for A x B straight up but the 89 says I can only solve for one variable. Any suggestions?

3. http://img.photobucket.com/albums/v407/ammad/sat2.jpg

This goes back to the inequalities, can the 89 titanium do this?

Thanks.

 

[TylerH]

1. No, the manual states the solve function only works for linear inequalities (and equalities, of course :tongue:).

2. This isn't the type of question a calculator can answer, because you aren't given enough equalities to find the answer in a straight forward way (you need 2, for 2 variables). This question relies on you being able to find the 2 integers that work. My approach: $$\left(a^{\frac{1}{2}}b^{\frac{1}{3}}\right)^6=a^3b^2=432=2*2*2*2*3*3*3=3*3*3*4*4=3^3*4^2$$

 

[MATLABdude]

I'm not sure if you can or cannot transfer the Titanium software (Hardware version 3) to the original TI-89 (Hardware versions 1 and 2). I'd bet not.

While you can't solve for inequalities, you CAN solve for equalities, and then "test" around the solutions to figure out where your intervals actually lie. Sketch the solutions out on a number line and then you can figure out which intervals are relevant:
http://www.sparknotes.com/math/algebra1/inequalities/section4.rhtml

As for your second question, you do not need a calculator. Here's a hint: simplify the equation, and then prime factorize 432. Show your work, and we can help you along. Remember, a and b are both positive integers.

 

[iibogo]

ah i see it now..

i would get

x^3 x y^2 = 3 x 3 x 2 x 2 x 2 x 2

which makes x = 3 and y = 4.

i understand, however just to clarify, the TI-89 would not be able to solve problems like these that ask for x times y or things like that? I just wanted to know because it would be great to save time on these problems.

 

[MATLABdude]

While the TI-89 can solve linear systems of equations (e.g. x+y=2, x+3y=-1), I don't believe you can generally solve (simple) non-linear systems (where you have several variables involving powers, exponents, etc.)

In any case, this is more of a conceptual problem, rather than a plug and chug: how do you tell the TI-89 that you need to have positive integers as a solution? You have only one equation involving two variables (an infinite number of solution pairs), and a set of criteria that then narrow it down to a single set.

Don't take this as chastising: calculators make it very easy to do computation, but can't substitute for the understanding. I've been there and done that and had to go back and develop the intuition that I probably should have learned the first go-around.

From what I recall of the math SAT (and this was over a decade ago) you only ever need a calculator for calculating trig ratios and simple arithmetic. I don't seem to recall ever needing the functionality of a TI-8X (Titanium, Voyager, etc.) and often, it was a detriment. Remember, a great number of high school students (even in the US, let alone internationally) can't afford a fancy graphing calculator.

If you're preparing, my best advice would be to practice, practice, practice (get a feel for the pacing and type of question: don't dwell on specific questions, either in practice and certainly not on the test). And while practicing, do the math portion with only with a basic scientific calculator to get it down cold.

Good luck!

 

[Lichdar]

I am a certified Kaplan instructor for the SAT.

You will not need any advanced calculator for the SAT; if you /need/ a calculator for any question, then you are most likely solving the problem incorrectly and are using far more time that you require.

 

[iibogo]

Thank you for your input and I definitely see where you are coming from but I would have to respectfully disagree. Though you might not ever need an advanced calculator on the SAT, having one puts you at an advantage if you know how to use it. I have taken several practice tests and the TI 89 CAS system has solved the problem way faster than I would have been able to had I not used it. Of course you have to pick and choose what problems you use it for but the TI-89 destroys most algebra problems on the SAT and can save you a lot of time.

Knowing fundamentals definitely trumps everything and I agree with you on that point but to save time, a TI-89 is beneficial. I am trying to see what the TI-89 can and cannot do so I can limit certain problems to use for the TI-89 and others to do by hand.

Thanks for you replies guys.

 

[Ele38]

I took the SAT last December, if you want an advice, do not bring with you any graphical calculator: I lost a lot of time using mine.