# Lesson 7

Spreadsheet Computations

Let's use spreadsheets as calculators.

### 7.1: Dust Off Those Cobwebs

- A person walks 4 miles per hour for 2.5 hours. How far do they walk?
- A rectangle has an area of 24 square centimeters. What could be its length and width?
- What is the area of this triangle?

### 7.2: A Spreadsheet Is a Calculator

Use a spreadsheet to compute each of the following. Type each computation in a new cell, instead of erasing a previous computation.

- \(2+7\)
- \(2−7\)
- \(7 \boldcdot 2\)
- \(7^2\)
- \(7 \div 2\)

- \(\frac17\) of 91
- \(0.1 \boldcdot 2+3\)
- \(0.1(2+3)\)
- \(13 \div \frac17\)
- The average of 2, 7, 8, and 11

### 7.3: Use the Contents of a Cell in a Calculation

- Type any number in cell A1, and another number in cell A2. Then in cell A3, type =A1+A2. What happens?
- In cell A4, compute the product of the numbers in A1 and A2.
- In cell A5, compute the number in A1 raised to the power of the number in A2.
- Now, type a new number in cell A1. What happens?
- Type a new number in cell A2. What happens?
- Use nearby cells to label the contents of each cell. For example in cell B3, type "the sum of A1 and A2." (This is a good habit to get into. It will remind you and anyone else using the spreadsheet what each cell means.)

### 7.4: Solve Some Problems

For each problem:

- Estimate the answer before calculating anything.
- Use the spreadsheet to calculate the answer.
- Write down the answer and the formula you used in the spreadsheet to calculate it.

- The speed limit on a highway is 110 kilometers per hour. How much time does it take a car to travel 132 kilometers at this speed?
- In a right triangle, the lengths of the sides that make a right angle are 98.7 cm and 24.6 cm. What is the area of the triangle?
- A recipe for fruit punch uses 2 cups of seltzer water, \(\frac14\) cup of pineapple juice, and \(\frac23\) cup of cranberry juice. How many cups of fruit punch are in 5 batches of this recipe?
- Check in with a partner and resolve any discrepancies with your answer to the last question. Next, type 2, \(\frac14\), \(\frac23\), and 5 in separate cells. (You may find it helpful to label cells next to them with the meaning of each number.) In a blank cell, type a formula for the total amount of fruit punch that uses the values in the other four cells. Now you should be able to easily figure out:
- How much in 7.25 batches?
- How much in 5 batches if you change the recipe to 1.5 cups of seltzer water per batch?
- Change the ratio of the ingredients in the fruit punch so that you would like the flavor. How many total cups are in \(\frac12\) batch?

### Summary

A spreadsheet can be thought of as a type of calculator. For example, in a cell, you could type \(=2+3\), and then the sum of 5 is displayed in the cell. You can also perform operations on the values in other cells. For example, if you type a number in A1 and a number in A2, and then in A3 type \(=A1+A2\), then A3 will display the sum of the values in cells A1 and A2.

Famliarize yourself with how your spreadsheet software works on your device.

- On some spreadsheet programs, an = symbol must be typed before the expression in the cell. (On others, it does not matter if your expression begins with =.)
- Know how to "submit" the expression so the computation takes place. If your device has a keyboard, it's likely the enter key. On a touchscreen device, you may have to tap a check mark.
- Learn symbols to use for various operations, and how to find them on your keyboard. Here are the symbols used for some typical operations:
- + for add
- - for subtract or for a negative number (this symbol does double duty in most spreadsheets)
- * for multiply
- / for divide
- \(a\) / \(b\) for the fraction \(\frac{a}{b}\)
- ^ for exponent
- . for a decimal point
- ( ) to tell it what to compute first. (often needed around fractions)