Chapter 7.6, Problem 34PPS

(a)

To determine

To write: two inequalities comparing the percent of increase from 1970 to 1980 to the percent of increase from 1980 to 1990.

Answer to Problem 34PPS

The price of milk in 1970 < the price of milk in 1980 and the price of milk in 1980 < the price of milk in 1990.

Explanation of Solution

Given information:

You will examine percent of change over time. The table gives the price of milk for various years.

  

Calculation:

The percent increase from 1970 to 1980:

  $\begin{array}{c}\text{percent}\text{of}\text{change=}\frac{\text{amount}\text{of}\text{change}}{\text{original}\text{amount}}\\ =\frac{\left(1.60-1.23\right)}{1.23}\\ =\frac{0.37}{1.23}\\ \gg 0.30\\ \gg 30\%\end{array}$

The percent increase from 1980 to 1990:

  $\begin{array}{c}\text{percent}\text{of}\text{change=}\frac{\text{amount}\text{of}\text{change}}{\text{original}\text{amount}}\\ =\frac{\left(2.15-1.60\right)}{1.60}\\ =\frac{0.55}{1.60}\\ \gg 0.34\\ \gg 34\%\end{array}$

So, the price of milk in 1970 < the price of milk in 1980 and the price of milk in 1980 < the price of milk in 1990.

(b)

To determine

To graph: the prices of milk over the years.

Explanation of Solution

Given information:

Use the $x$ axis as the years and $y$ axis as the prices.

Calculation:

The graph of the price of milk over years:

  

(c)

To determine

To find: the decade had the greatest percent of increases in the price of milk.

Answer to Problem 34PPS

The decade is 1980-1990.

Explanation of Solution

Consider the graph from part (b),

  

From the above graph you can see that 1980-1990 had the greatest percent of increases in the price of milk.