Excel for the Math Classroom

Preface

This book was born out of a desire to help teachers teach their students math by being engaged in its study, and by showing teachers how they can custom-build visual examples of some of the concepts they are trying to get across to their students. Microsoft Excel is an extremely powerful spreadsheet with literally hundreds of built-in mathematical, statistical, and other functions to accomplish the mundane calculations encountered in the world of business. However, the Excel program has tools and features hidden in arcane menus that do not enable self-discovery. A person using Excel often thinks, there MUST be a way to do this, but where would they have hidden it?.

Our hope is that this book will help you to discover more features available in Excel and your students to become better at mathematics by using Excel. If you are also inspired to alter, refine, or completely redesign what you will find in here, even better. And, if you would rather not spend a lot of time trying to learn Excel, you can download all these files in their completed state by going to the secret web page at http://www.MrExcel.com/mathfiles/html .

One final note to Mac users: all of our screen shots were done using the Windows version of Excel 2003. Instructions for the Mac should be similar, except that the Windows right-click on the Mac is accomplished by holding down the Control key on the keyboard while clicking on the right mouse button.

Bill Hazlett

Bill Jelen

Calculation Basics

Excel is great at doing math. When Dan Bricklin conceived of the first spreadsheet in 1978, he envisioned a calculator where you could set up a math problem, but then scroll backwards in time and change the terms in the problem to see a new answer. Along with Bob Frankston, he developed VisiCalc – a Visible Calculator. Since VisiCalc in 1979, all spreadsheets have been able to calculate.

This section will teach you the basic math operators and the functions available for demonstrating classroom math.

There are at least three common methods of entering formulas. In the first three examples below, you will learn these three methods of entering formulas. You can then choose whichever method is the easiest for you.

Using the Touch-Typing Method (Addition)

Figure 1 shows a story problem. You want to enter a formula in cell B6 that will add cells B4 and B5.

Figure 1

Solving an addition story problem in Excel with touch-typing

Start your formula with an equals sign.

With the mouse, single click in cell B6 to move the cellpointer to that cell. Every formula must start with an equals sign, so type the equals sign to start entering the formula.

Figure 2

Always start a formula with an equals sign.

Type in the rest of the formula.

In this example, you will use the Touch-typing method of entering the formula. Without typing any spaces, finish typing the formula as follows: B4+B5

Figure 3

Using a formula to add values in two cells

Press Enter to tell Excel that the formula is complete.

When your screen looks like Figure 3, press the Enter key on the keyboard. After you type Enter, Excel will calculate that the sum is 30. Excel will also move the cellpointer down one cell to B7.

Figure 4

Pointer automatically moves down one cell when calculation is done.

Look at the formula.

Press the Up arrow one time to move the cellpointer back to cell B6. When B6 is selected, look at the formula bar just above the spreadsheet. Although the spreadsheet shows a value of 30 in the cell, the formula bar reveals that this cell actually contains a formula of =B4+B5.

Figure 5

Formula bar displays the formula used to derive the value in a cell.

See how the formula result changes when the elements change.

Here is the miracle of spreadsheets. Move the cellpointer up to cell B4 and type a different number instead of the 20. Type 200 and press Enter. The cellpointer will move down to cell B5, but all formulas that reference B4 in the entire worksheet will instantly recalculate. Thus, cell B6 becomes 210.

Figure 6

A formula’s value automatically updates when any cells referenced in that formula change.

Using the Mouse Method (Subtraction)

Figure 7 shows a subtraction story problem. In this case, you will want to set up a formula that subtracts B5 from B4. In this example, you will use the Mouse method for entering parts of the formula.

Start your formula with an equals sign.

As before, you have to type the equals sign on the keyboard to start the formula.

Figure 7

Formulas start with an equals sign

Select the first term.

After typing the equals sign, use the mouse to touch cell B4. Because you are in formula entry mode, the formula in cell B6 automatically types B4 for you.

Figure 8

Solving a subtraction problem in Excel using the mouse

Enter a minus sign.

Now, back on the keyboard, type the minus sign. Notice that when you type the minus sign, the flashing dots around B4 become a solid blue color. Excel is waiting for you to touch another cell with the mouse.

Figure 9

A solid blue box indicates that Excel is waiting for your input.

Select the second element.

With the mouse, touch the 30 in cell B5. Excel will enter B5 in the formula.

e9781615473151_i0011.jpg Tip:

If your keyboard has a numeric keypad, the upper right keys on the keypad will let you type the common operator keys without using the Shift key.

Figure 10

Excel automatically enters the cell location you click on with the mouse.

Press Enter to tell Excel that the formula is complete.

When you type the Enter key, Excel calculates the result.

Figure 11

Excel calculates the result and automatically moves the cursor down one cell.

If you are comfortable using the mouse, this technique of entering formulas is fairly quick and easy.

Using the Arrow Key Method (Addition and Subtraction)

The next story problem requires both addition and subtraction. The Arrow key method was introduced in 1981 by Lotus 1-2-3. The method became very popular for accountants who hated typing obscure cell references like B4 and AJ62. This was before computers typically had a mouse (the first Macintosh didn’t come out until late 1983).

Start your formula with an equals sign.

As shown in the image below, type an equals sign in cell B7.

Figure 12

Solving a subtraction problem in Excel using the arrow keys

Select the first element.

Using the arrow keys on your keyboard, type the Up arrow key three times. After the first press of the Up arrow key, the screen will think that you want to start your formula as =B6.

Figure 13

Screen after pressing the Up arrow key once

That is OK. Ignore the screen and press the Up arrow key a second time. Now the screen thinks that you must want to start your formula with =B5.

Figure 14

Screen after pressing the Up arrow key twice

Again, ignore what is on the screen and type the Up arrow key one more time. Now the screen suggests that your formula should start with =B4. This is correct.

Figure 15

Screen after pressing the Up arrow key thrice

Enter a plus sign to the first element.

The next part is a little tricky. In your formula, you want to add B5 to the formula. Type the plus sign on your keyboard. This tells Excel that you are accepting the B4 portion of the formula and that you are ready to enter another cell. Instead of a flashing box around B4, you now have a solid box around B4. Here is the tricky part: as soon as you type the plus sign, Excel returns the focus back to the original cell location of B7.

Figure 16

The flashing box turns solid blue when you accept a portion of the formula by typing the plus sign

Select the second element.

You want to point to the 3 in cell B5 now. Many people trying this method for the first time think that they should type the Down arrow to move down from B4. This is not correct. You actually have to type the Up arrow twice to move up from cell B7 to B5.

Type the Up arrow twice and Excel will propose a formula of =B4+B5.

Figure 17

Excel proposes the next element in the formula

Enter a minus sign and select the third element.

Next, type the minus sign on the keyboard. Excel will return the focus to the original location of B7. Press the Up arrow one time to subtract B6 from the formula.

Figure 18

Selecting the next element

Press Enter to tell Excel that the formula is complete.

When you type Enter, Excel calculates an answer of 3. Move the cellpointer back to B7 to examine the formula in the Formula bar.

Figure 19

Completed formula

Now that you have learned the three methods for entering formulas, you can use whichever method suits you the best. In the remaining sections of this chapter, you will see the formulas to use for various mathematical operations. You can use whichever method you prefer for entering these formulas.

e9781615473151_i0022.jpg Note:

Once you get used to the arrow key method, it is the absolute fastest way to enter formulas. The act of moving your hands from the keyboard to the mouse then back to the keyboard is relatively slow. The process to enter the formula above requires only nine keystrokes, and many of those are repetitive strokes of the Up arrow.

Entering Multiplication Problems

Problems requiring multiplication use the Asterisk key for the multiplication operator. Type an asterisk using the Shift+8 keys or the Asterisk key on the numeric keypad.

Yes – it would be a lot easier if they used the X key for multiplication, but then it could become confusing whether the X was referencing a cell location, as in X2, or was meant to multiply by 2.

Figure 20

Multiplication problems use an asterisk

Entering Division Problems

There are two slash signs on the keyboard. File paths in Windows typically require the backslash, located above the Enter key. Luckily, division problems require the forward slash, located on the same key as the question mark. The image below shows a division problem.

Figure 21

Division problems use a forward slash

Entering Fraction Problems

Sometimes Excel expects your students to understand higher mathematical concepts, such as that a fraction is really a division problem. That is, one-ninth is actually one divided by nine. For fractions in Excel, enter the numerator, the forward slash, and the denominator, as seen in the formula bar in Figure 22.

Figure 22

Expressing fractions as division problems

Using Parentheses to Control the Order of Operations

When it comes to math operating signs in an Excel formula, Excel understands and uses the order of operations correctly. It does not necessarily move from left to right within the formula. Instead, it follows the old mnemonic phrase Please Excuse My Dear Aunt Sally: Parentheses (P) and other grouping symbols take precedence, followed by Exponents (E). Next, Multiplication (M) and Division (D) are done in order from left to right, and then Addition (A) and Subtraction (S), also from left