Why this has a page of its own. The calculator is not a topic on the test. It is a tool you use inside every topic, and the minutes it costs you when you do not know it are taken from all fourteen families at once. An hour spent here is worth more than an hour spent on any single family.
The calculator is a TI-30XS MultiView, and you have a choice about it. You can bring your own, or you can use the one that appears on the screen — the testing center provides it, and it is the same machine either way.
On the Mathematical Reasoning test it is there for all but the first few questions, and the formula sheet is there the whole way through. You can use it on the Science test as well.
Whichever you choose, the mistake to avoid is meeting it for the first time on the day. It is not a hard machine. It is an unfamiliar one, and unfamiliar costs minutes.
There is a free version of the same calculator that runs in a browser, with no account and nothing to install:
- The TI-30XS MultiView, online · exactly the on-screen calculator they give you at the testing center. Open it beside any quiz on this site and do the arithmetic on it rather than in your head or on your phone.
That last sentence is the whole method. You do not study a calculator; you use one until your fingers know it. Every quiz and every worksheet here is a chance to practice on the machine you will actually sit with.
- 17 minIntro to the TI-30XSScot Smith. The keys, the screen, and what the second function button is for. Start here.
- 43 minGED Calculator: How to Use ItWeiss Videos. The long one, and the best one. If you watch only one, watch this. Worth doing with the online calculator open in another window so you can follow along.
- 9 minIntro to the GED Test on-screen calculatorGED Testing Service, the people who make the test. Short, and specifically about the on-screen version.
Nearly everything on this calculator you will find by hunting for it, and that is fine. One menu is worth learning deliberately, because the test asks something it answers and the formula sheet gives you nothing for it.
Press the PRB key and you get a short menu. Three of its entries do the counting that family 9 is about:
- nPr · permutations. How many ways a number of things can be arranged when the order matters — who comes first, second and third in a race. Type the total, press PRB, choose nPr, type how many you are taking, press enter. Eight runners taking the three medal places: 8, PRB, nPr, 3, enter — and the answer is 336.
- nCr · combinations. How many ways they can be chosen when the order does not matter — which three people are on the committee, with no first or second about it. Same keystrokes, nCr instead: 8, PRB, nCr, 3, enter — and the answer is 56, because each group of three was counted six times over in the 336.
- ! · factorial. The product of every whole number from 1 up to the one you typed. 4! is 4 × 3 × 2 × 1 = 24, which is the number of ways four things can be put in order.
Why this is worth the two minutes. The GED’s own list of what it tests says, in these words, “use counting techniques to solve problems and determine combinations and permutations.” But no formula for either one is printed on the formula sheet, and the word factorial does not appear in the test’s published description at all. The machine does them instead. So the thinking the test is actually asking for is the one question in italics above — does the order matter? — and the arithmetic is three keystrokes.
These questions are not common. Probability and counting share one part of the test with geometry and statistics, so you may sit the whole exam without meeting one. But if you do meet one, it is a mark you can have for the cost of knowing where this menu is.
Quiz 34, Favorable Outcomes, teaches the counting itself, by hand and by listing, so that the calculator is a shortcut rather than a substitute.
- Light & Salt Learning: TI-30XS tutorials · forty short videos, one job each. Not meant to be watched through; meant to be searched when you hit something you cannot make the calculator do.
- Minnesota Literacy Council: the written tutorial · a PDF, keystroke by keystroke. Print it and keep it beside you while you work.
You do not need to buy one — the on-screen calculator is provided, and the free online version is the same machine. But some people work better with buttons under their fingers, and you are allowed to bring your own.
It is a common calculator, carried by the big stores — Walmart, Best Buy, Staples — and sold online. Two listings, if it helps to see what you are looking for:
- Texas Instruments TI-30XS MultiView · on Amazon.
- The same calculator · at Best Buy.
Check the name carefully before you buy. Texas Instruments makes several calculators with names close to this one, and the test specifies the TI-30XS MultiView.
The formula sheet is on the screen for the whole test, which means you are not asked to memorize the area of a circle or the Pythagorean theorem. What you are asked to do is recognize which formula a question wants, and put the right numbers into it.
It matters as much to know what the sheet leaves out. For the coordinate-geometry part of the test, Lines on the Grid lists both: the sheet gives you the slope formula, slope-intercept form, point-slope form, the Pythagorean theorem, the area and volume formulas, the quadratic formula, simple interest, and distance equals rate times time. It does not give you standard form, the midpoint, the distance between two points, or the order in which coordinates are written. Those four you carry in yourself.
The formula sheet has a page of its own — everything on it grouped by family, the longer list of what it does not give you, and the one line on it that is a trap.