Let P(x) be the number of people in the U.S. who own a cell phone x years after 1990. Your friend says that

$$P ( x + 1 ) > P ( x )$$

for any x because

$$x + 1$$

is always greater than x. Is your friend correct? Explain.

The distance travelled by an object when it begins at rest and experiences constant acceleration is one-half the acceleration multiplied by the square of the time. Create your own symbols to express this statement symbolically.

In a small group, discuss and actively work through the construction of the Pinwheel Pattern and prove that it has no rigid symmetries. After your discussion, write a brief narrative describing the construction and proof in your own words.

A cell phone sends signals at about $850 \mathrm{MHz}$ (where $1 \mathrm{MHz}=1 \times 10^6 \mathrm{~Hz}$ or cycles per second).
What is the wavelength of this radiation?

Complete the letter with the appropriate forms of the verbs in the parenthesis. Il _____ (travailler), mais il _____ (aimer) beaucoup mieux le sport et il _____ (parler) beaucoup au t$\'e$l$\'e$phone.

Refer to your questions and answers about the previous figure to help you answer the questions below.

a. Where might you find muscle pairs?

b. Describe how the muscles in your upper arm work together to bend and straighten your arm.

c. When exercising to build muscular strength, why is it important to exercise both muscles in a muscle pair equally?

Data Analysis The average monthly cellular phone bills $y$ (in dollars) for subscribers in the United States from $1990$ through $1999$, where $x$ is the year, are shown as data points $(x, y)$. (Source: Cellular Telecommunications Industry Association) \

$$\begin{array}{llll}(1990, & 80.90) & (1995, & 51.00) \\ (1991, & 72.74) & (1996, & 47.70) \\ (1992, & 68.68) & (1997, & 42.78) \\ (1993, & 61.48) & (1998, & 39.43) \\ (1994, & 56.21) & (1999, & 41.24)\end{array}$$

Use your model to estimate the average monthly cellular phone bill in $2005.$

Develop a model to predict the asking price of houses in Silver Spring, Maryland, based on living space, lot size, whether the has a fireplace, the number of bedrooms, the number of bathrooms, age, whether it has central air conditioning, the number of parking spaces, and whether the house has a brick exterior. Use the sample of 61 houses that is stored in SilverSpring as the data for this analysis.

a. Using all the data as a training sample, develop a regression tree model to predict the asking price of the house. .

b. What conclusions can you reach about the asking price of the house?

c. Using half the data as the training sample and the other half of the data as the validation sample, develop a regression tree model to predict the asking price of the house.

d. What differences exist in the results of (a) and (c)?

A cell phone signal that travels from coast to coast in the United States must travel approximately $3000$ miles (about $5 \times 10^6 \mathrm{~m}$ ). This signal is carried by different types of electromagnetic radiation (typically radio and microwaves) at a speed close to $c$. Is the approximate time required for your cell phone signal to propagate from coast to coast:

(a) $0.5 \mathrm{~s}$

(b) $3 \mathrm{~s}$

(c) $0.02 \mathrm{~s}$

(d) $0.0005 \mathrm{~s}$

Can you notice this time delay?

Adding Your Own Details. Rewrite the following sentences to make each one more Informative and descriptive. Add at least two different details to each. Mary walked the dog.

You sign up for an unlimited text messaging plan for your cell phone. The equation y = 20 represents the cost y (in dollars) for sending x text messages. Graph the equation. What does the graph tell you?

The cost of a cell phone for one month is a linear function of the number of minutes used. The total cost for 20,35 , and 40 additional minutes are displayed. What is the slope of the line represented in the table?

A 0.1

B 0.4

C 2

D 2.5

$$\begin{array}{|l|c|c|c|} \hline {}{}{\text { Cell-Phone Costs }} \\ \hline \begin{array}{l} \text { Number of } \\ \text { Additional Minutes } \end{array} & 20 & 35 & 40 \\ \hline \text { Total Cost } & \$ 48 & \$ 54 & \$ 56 \\ \hline \end{array}$$

Use the word $delicate$ to describe something you own or would like to own.

The first three digits of a university telephone exchange are 452. If all the sequences of the remaining four digits are equally likely, what is the probability that a randomly selected university phone number contains seven distinct digits?