Chapter 4.4, Problem 21PFA

To determine

To find: The month the skyscraper will reach its full height of 820 feet.

Answer to Problem 21PFA

The month the skyscraper will reach its full height of 820 feet is B. Month 30.

Explanation of Solution

Given information:

The equation of the line of fit is given from problem number 20 as

  $y=27x+9.$ (1)

Calculation:

The height of the skyscraper is given as 820 feet.

Therefore, plug in $y=820$ in equation 1, to get the corresponding value of x .

  $\begin{array}{l}\therefore 820=27x+9\\ \therefore 820-9=27x\\ \therefore 811=27x\\ \therefore x=\frac{811}{27}\\ \therefore x=30.03\end{array}$

i.e. $x\approx 30$

Conclusion:

So, the skyscraper will reach the maximum height of 820 feet in the 30th month.