Solve the following percentage problem. Between $2000$ and $2015$, the number of twin births in the United States increased by $13 \%$, to approximately $135,000$. About how many twin births were there in $2000$?

In the United States, the number of twin births is approximately 1 in 90. At a certain hospital let X be the number of births until the first twins are born. Find the first quartile, the median, and the third quartile of X.

Fill in the blanks in the following statements.

The wholesale price of a TV is $40 \%$ less than the retail price. Therefore, the wholesale price is $\underline{\qquad \qquad}$ times the retail price.

Fill in the blanks in the following statements.

Will is $22 \%$ taller than Wanda, so Will's height is $\underline{\qquad \qquad}\%$ of Wanda's height.

Among live deliveries, the probability of a twin birth is .02. (a) In 200 live deliveries, how many would be expected to have twin births? (b) What is the probability of no twin births? (c) One twin birth? (d) Calculate these probabilities both with and without an approximation. (e) Is the approximation justified? Discuss fully

Twin Births. The table below illustrates the upward trend in twin births. a) Model the data with a linear function. Let the independent variable represent the number of years after 1990 ; that is, the data points are $(0,93.8),(5,96.7)$, and so on. Answers may vary depending on the data points used. b) With the function found in part (a), estimate the number of twin births in 2009 and in 2012.

$$\begin{array}{|c|c|} \hline \text { Year, } x & \begin{array}{c} \text { Number of Twin Births, } \\ y \text { (in thousands) } \end{array} \\ \hline 1990,0 & \\ 1995,5 & 93.8 \\ 2000,10 & 96.7 \\ 2001,11 & 118.9 \\ 2002,12 & 121.2 \\ 2003,13 & 125.1 \\ 2004,14 & 128.7 \\ \hline \end{array}$$

According to modern science, Earth is about $4.5$ billion years old and written human history extends back about $10,000$ years. Suppose you represent the entire history of Earth by $12$ hours on a clock, with the birth of Earth at the stroke of midnight and today at the stroke of noon.

a. How much time on the clock represents $1$ billion years?

b. How long before noon does written human history begin?

According to modern science, Earth is about $4.5$ billion years old and written human history extends back about $10,000$ years. Suppose you represent the entire history of Earth with a $100$-meter-long timeline, with the birth of Earth on one end and today at the other end.

a. What distance represents $1$ billion years?

b. How far from the end of the timeline does written human history begin?

Solve the following percentage problem. In $2015$, alcohol use among high school seniors was down from the previous year by $5.6 \%$, to $35.3 \%$. What was the usage rate for the previous year ($2014$)?

Complete the following sentence. The life expectancy (at birth) of all Americans in $2014$ ( $78.8$ years) is__________ percent greater than the life expectancy in $1900$ ($47.3$ years).

Solve the following percentage problem. The total (after-tax) cost of a laptop computer is $\$ 1278.24$. The local sales tax rate is $7.6 \%$. What is the retail (pre-tax) price?

Solve the following percentage problem. A store purchase lawnmowers from the manufacturer and marks up the price by $40 \%$ to arrive at a retail price. Fill in the blank: The wholesale price is times the retail price.

Find out the absolute change and the relative change in the following case. The number of commercial U.S. oldies radio stations decreased from $729$ in $2006$ to $351$ in $2016$.

Assume that $30\%$ of city employees in Carson City ride the bus to work. Consider the following two statements:

• The percentage of city employees who ride the bus to work is $10 \%$ higher in Freetown than in Carson City.

• The percentage of city employees who ride the bus to work is $10$ percentage points higher in Freetown than in Carson City.

For each case, state the percentage of city employees in Freetown who ride the bus to work. Briefly explain why the two statements have different meanings.