Cracking the SAT

Part III

How to Crack the Math Section

Chapter 10

The Calculator

A calculator is an important tool on the SAT. ETS states that the SAT contains no questions requiring you to use a calculator, but it also says that students are strongly encouraged to take a calculator. We agree; a calculator is a reliable tool to use and it is a good idea to have one for the Math sections of the SAT. This chapter will introduce some basic information about how and when to use your calculator most effectively on this test.

You are allowed (but not required) to use a calculator when you take the SAT. You should definitely do so. A calculator can be enormously helpful on certain types of SAT math problems. This chapter will give you general information about how to use your calculator. Other math chapters will give you specific information about using your calculator in particular situations.

You’ll need to take your own calculator when you take the SAT. If you don’t own one now, you can buy one for around $15 or less, or you can ask your math teacher about borrowing one. If you do purchase one, buy it far enough ahead of time to practice with it before you take the test. Even if you now use a calculator regularly in your math class at school, you should still read this chapter and the other math chapters carefully and practice the techniques we describe.

Gee, ETS Must
Really Like Me

Why else would it let you
use a calculator? Well,
friend, a calculator can
be an obstacle at times.
ETS hopes that many test
takers will waste time using
their machines to add
3 + 4. When it comes to
simple calculations, your
brain and pencil are faster
than the fastest calculator.

Make sure that your calculator is either a scientific or a graphing calculator. It must perform the order of operations correctly. To test your calculator, try this problem. Type it in to your calculator exactly as written without hitting the enter or equals key until the end: 3 + 4 × 6 = . The calculator should give you 27. If it gives you 42, it’s not a good calculator to use.

Many students already own a graphing calculator. If you have one, great; if you don’t, don’t sweat it. Graphing calculators are not necessary on the SAT. However, if you have one, it may simplify certain graphing problems on the SAT.

If you do decide to use a graphing calculator, keep in mind that it cannot have a QWERTY-style keyboard on it (like the TI-95). Most of the graphing calculators have typing capabilities, but because they don’t have typewriter-style keyboards, they are perfectly legal.

Also, you cannot use the calculator on your phone. In fact, on test day, you will have to turn your phone off and put it underneath your seat.

The only danger in using a calculator on the SAT is that you may be tempted to use it in situations in which it won’t help you. Joe Bloggs thinks his calculator will solve all his difficulties with math. It won’t. Occasionally, it may even cause him to miss a problem that he might have answered correctly on his own. Your calculator is only as smart as you are. But if you practice and use a little caution, you will find that your calculator will help you a great deal.

Here is a complete list of what a calculator is good at on the SAT.

·        Arithmetic

·        Decimals

·        Fractions

·        Square roots

·        Percentages

·        Graphs (if it is a graphing calculator)

We’ll discuss the calculator’s role in most of these areas in the next few chapters.

Adding, subtracting, multiplying, and dividing integers and decimals is easy on a calculator. You need to be careful only when you key in the numbers. A calculator will give you an incorrect answer to an arithmetic calculation only if you press the wrong keys.

Calculators Don’t Think

A calculator crunches
numbers and often saves
you a great deal of time
and effort, but it is not a
substitute for your
problem-solving skills.

The main thing to remember about a calculator is that it can’t help you find the answer to a question you don’t understand. If you wouldn’t know how to solve a particular problem using pencil and paper, you won’t know how to solve it using a calculator either. Your calculator will help you, but it won’t take the place of a solid understanding of basic SAT mathematics.

Before you use your calculator, be sure to set up the problem or equation on paper; this will keep you from getting lost or confused. This is especially important when solving the problem involves a number of separate steps. The basic idea is to use the extra space in your test booklet to make a plan, and then use your calculator to execute it.

Working on scratch paper first will also give you a record of what you have done if you change your mind, run into trouble, or lose your place. If you suddenly find that you need to try a different approach to a problem, you may not have to go all the way back to the beginning. This will also make it easier for you to check your work, if you have time to do so.

Don’t use the memory function on your calculator (if it has one). Because you can use your test booklet as scratch paper, you don’t need to juggle numbers within the calculator itself. Instead of storing the result of a calculation in the calculator, write it on your scratch paper, clear your calculator, and move to the next step of the problem. A calculator’s memory is fleeting; scratch paper is forever.

Write Things Down

You paid for the test
booklet; make the most
of it. Keep track of your
progress through each
problem by writing down
each step.

In Chapter 11, we will discuss the proper order of operations when solving equations in which several operations must be performed. Be sure you understand this information, because it applies to calculators as much as it does to pencil-and-paper computations. You may remember PEMDAS from school. PEMDAS is the order of operations. You’ll learn more about it, and see how questions on the SAT require knowing the order of operations, in Chapter 11. You must always perform calculations in the proper order.

Most scientific calculators have buttons that will automatically simplify fractions or convert fractions from decimals. (For instance, on the TI-81, TI-83, and TI-84, hitting “Math” and then selecting the first option, “Answer –> Fraction,” will give you the last answer calculated as a fraction in lowest terms.) Find out if your calculator has this function! If it does, it is often easier to simplify a messy fraction with your calculator than by hand. This function is also very useful when you get an answer as a decimal, but the answer choices given are all fractions. (For Grid-In questions, it is not necessary to reduce a fraction to its simplest form.)

Change the batteries to your calculator a week before the SAT so that you know your calculator won’t run out of power halfway through the test. You can also bring extra batteries with you, just in case. Although it isn’t very likely that the batteries will run out on your calculator on the day of the test, it could happen, so you may as well be ready.

Remember that the test makers allow you to have a calculator when you’re taking the SAT. They know you have one. They also know that they have created many questions in which the calculator is worthless (for example, visual counting problems, wordy logic problems, and many questions that are so wordy and deceptive that reading carefully is a much more important skill than properly using a calculator). So be sure to read math questions fully—they will have some serious surprises in there. Finally, use your calculator wisely, and remember that sometimes you won’t be able to use it at all.

·        You should definitely use a calculator on the SAT.

·        Take your own calculator when you take the test. You don’t need a fancy one. Make sure your calculator doesn’t beep or have a typewriter-style keyboard.

·        Even if you already use a calculator regularly, you should still practice with it before the test.

·        Be careful when you key in numbers on your calculator. Check each number on the display as you key it in. Clear your work after you finish each problem or after each separate step.

·        A calculator can’t help you find the answer to a question you don’t understand. (It’s only as smart as you are!) Be sure to use your calculator as a tool, not a crutch.

·        Set up the problem or equation on paper first. By doing so, you will eliminate the possibility of getting lost or confused.

·        Don’t use the memory function on your calculator (if it has one). Scratch paper works better.

·        Whether you are using your calculator or paper and a pencil, you must always perform calculations in the proper order.

·        If your calculator runs on batteries, make sure it has fresh ones at test time! Change them a week before.