TI-84 Circumference Trick: Solve ACT Figure-Eight Problem FAST

Solve this ACT figure-eight circle problem much faster using your TI-84 and the circumference program.

In this video, I show you how to calculate the total distance around two tangent circles quickly, then divide by the train’s speed to find the travel time — without hand-writing any formulas.

If you haven’t created the TI-84 circumference program yet, check out my TI-84 Calculator Programs playlist where I walk you through how to build it step-by-step.

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🧠 About My2tor
I’m Tina Wiles, test anxiety expert and founder of My2tor & ACTSATPrepHQ.com.
I help students master the mindset, strategy, and content they need to succeed on high-stakes exams like the ACT and SAT.

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⏱ Timestamps
00:00 Intro
00:09 Understanding the figure-eight circle setup
00:17 Diameters → radii
00:31 Why we need total circumference
00:51 Running the TI-84 circumference program
01:14 Using the diameter to get radius
01:42 Running it again for the second circle
01:54 Adding circumferences
02:22 Converting distance to time
02:36 Final answer + outro

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