You learn to speak by speaking. to study by studying, to run by running, to work by working -Anatole France 3.1 Deciding to Run Focus Problem animal can maintain its top speed for only a certain distance. You can use that distance to determine how long the animal can run and, therefore, how much time it has to catch you How far can you run in that time? When you calculate the head start that you would need, you are determining the minimum safe distance to be away from that animal. This is useful information to know before heading into that animal's natural habitat. Choose one of the animals listed in the table and write an equation to model its distance run vs. time. Write a separate equation to model your distance from the animal vs. time. Graph both of these equations on the same coordinate grid If you have ever spent any time in a wilderness area, you have likely wondered about the animals there and your safety. Could you stumble upon a bear on a path in the woods? Could you accidentally come between a moose and her calf? What should you do? It's said that you should never run from a bear, for example, but is that always true? What if the bear is far enough away from you that you think you can get away before it catches you? How far away would you need to be in order to be safe? Obviously, any serious consideration or calculation has to be done well before you actually encounter a wild animal and must face this decision. We know the top speed at which many animals can run, and we know how long they are able Explain how the graphs illuminate the situation. What does to maintain that top speed. This information is shown in thethe slope represent? Where do the graphs intersect, and table for a few animals. how do you interpret that point? What do the y-intercepts represent? Top Speed Distance at Finally, choose another animal that you are interested in and find the minimum safe distance from it. Polar bear Black bear Lion Moose Rhinocero5 Animal (miles per hour) Top Speed 20 25 30 l mile 2 miles 48 meters 400 meters 100 meters When we're considering running from a wild animal or head- ing into its natural habitat, we have to consider WHEN IS IT Let's assume that the average person can run 10 miles per hour (at least for short distances while being chased). Let's also assume that a person and an animal each achieve top This focus problem can be solved in many different but related ways. You might begin by trying to understand the though, you might discover that representing the informa- ne how much of a head start you From which animal from each animal listed in the issues numerically by "running the numbers." At some point, table if it was chasing you at full speed. would you need the greatest head start? Consider that each tion in equations might be more efficient. And, if you're

trying to explain what you've discovered about the issues to determining when it is worth it to use algebraic methods. someone else, a graph might be the most useful way to do it. Other times, the question will relate to particular contexts It's important that you can use multiple representations not such as buying a hybrid vs. gas-powered car or buying an only to solve a problem but also to explain your solution to an audience. This is true for the focus problem as well as for tools that you can use to answer this type of question. many other problems that you'll solve during this cycle. e-reader vs. books. By the end of the cycle, you'll have many The question "When is it worth it?" will be the focus of the third cycle of the book. Sometimes the focus will be on You will see periodic sticky notes throughout the cycle to encourage you to keep working on your solution to this prob- lem as you learn new methods to apply.