How to use your TI-84 calculator to ace the SAT or ACT

Until the new SAT unrolls––with its much-feared no-calculator section––it behooves students prepping for this and other all-important college admissions tests (like the ACT) to learn the ins and outs of their most powerful ally on the SAT Math section.

Choosing a calculator.

First things first: what calculators are and are NOT allowed on the SAT and ACT? The short answer is that pretty much anything without a QWERTY keypad is allowed on the SAT, and anything under a TI-89 is allowed on the ACT. (For more info, consult the College Board stipulations for calculator usage on the SAT and similar policies for the ACT.) Having tutored both test for years, I find a TI-84 Plus is the sweet spot: not too fancy, often required for most high school math classes anyway, and contains all the power and functionality you’ll need for either SAT or ACT Math sections.

When I teach students how to leverage their TI calculators for success on the SAT and ACT, their most often quoted reply is “Wow–I never knew I could do that!” Whether or not your high school curriculum utilizes calculators all the time or once in a blue moon, there are a few essential features every SAT and ACT test-taker needs to know about:

1. Math > Frac.

Oftentimes, the SAT or ACT will give simplified, algebraically-derived fractions in the answer set, whereas the most efficient path to the correct answer is through decimal calculations. Facility with conversion back and forth between decimal numbers and their fractional equivalents is crucial not only to avoiding tedious algebra, but also navigating through answer choices to eliminate “nonsense” answers. I place the Math > Frac technique at the top of the list primarily because I use it so dang frequently!

Here’s how to use this feature on the TI-84 Plus:

1. Locate the number you need to convert to a fraction and bring it to the home screen, either by typing, by 2nd > ANS, or by selecting the number and hitting ENTER.

2. Hit MATH > NUM > Frac, and the decimal answer will be converted to the most reduced form of the fraction. If the decimal number reappears unchanged, this means that the number is irrational, or unable to be represented fractionally.

2. The graphing functionality.

This is probably the most underused feature of SAT and ACT students’ calculators. I regularly tutor students whose attempt to manually draw and graph lines and parabolas in the coordinate plane not only suck up precious time on math problems, but are often skewed and not drawn to scale––thereby jeopardizing the accuracy of their answers.

Here are some common scenarios where utilizing the graphing functionality of your calculator is the most effective problem-solving method:

  • Solving a system of two equations: GRAPH > input equations > CALC > Intersect.
  • Finding the critical points of a parabola: GRAPH > input equations > CALC > zeros or minimum or maximum.
  • Extrapolating a function or equation with a table of values: GRAPH > input equations > TABLE. Pro Tip: Oftentimes, you’ll want to calibrate the x-values. To do so, hit TBLSET and edit the ∆Tbl entry accordingly.

Of course, there are many other uses to the graphing functionality. Both SAT and ACT typically present visual answer choices (e.g., “Which of the following is the graph of the function in the coordinate plane?”), so all you need to do if you have a TI-84 calculator is graph it and select the answer that looks like your screen!

3. Applications.

Most TI-84 calculators come equipped with a suite of applications (found via the purple APPS button) with basic tutorials on conic sections (APPS > CONICS), number sense and linear algebra (APPS > ALG1PRT1), and area formulas for obscure polygons (APPS > AreaForm). A lesser-used app is Inequalz, for graphing inequalities in the coordinate plane (ACT usually has at least one problem on this..).

In addition to these stock applications, many more helpful apps and programs can be found on the internet. Just plug your TI-84 USB cord into your computer and your calculator, download these helpful resources, and transform your handheld into a SAT or ACT Math lightsaber. TICalc.org is the website of choice for such programs. (Pro tip: Look under Archives > File Archives > 84plus > basic > math.)

Finally, I’ve written my own SAT and ACT Math program for the TI-84 calculator, replete with concrete tips and helpful formulas. I give it complimentary to all North Avenue test prep students. It’s an essential part of North Avenue’s SAT or ACT test prep program!

 

Interested in learning more about North Avenue’s SAT and ACT test prep tutors? Contact us today to book a free, 30-min. SAT/ACT test prep consultation.

For further reading, be sure to check out this article from Calcblog: SAT Calculator Stratgies.

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