The ratio of scale model of a boat to a real boat is
![\frac{1\text{ in}}{4\text{ ft}}](https://img.qammunity.org/2023/formulas/mathematics/college/mpe8nzycmh64z64hixs0xy5rwj48bxvx8z.png)
Part A:
Using that ratio, if the height of the real boat is 28 feet, then we can solve it by
![\begin{gathered} \text{Let }x\text{ be the height of the boat in scale model} \\ \frac{x\text{ in}}{28\text{ ft}}=\frac{1\text{ in}}{4\text{ ft}} \\ x\text{ in }=\frac{28\text{ ft}\cdot1\text{ in}}{4\text{ ft}} \\ x\text{ in }=\frac{28\cancel{\text{ ft}}\cdot1\text{ in}}{4\cancel{\text{ ft}}} \\ x\text{ in }=7\text{ in} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/4129oxvb6rjnpnwdlh3d9d9j58bps8arlg.png)
Therefore, the height of the boat in scale model is 7 inches.
Part B:
Using the same method as above, we have the following
![\begin{gathered} \text{Let }y\text{ be the length of the real boat} \\ \frac{5\text{ in}}{y\text{ ft}}=\frac{1\text{ in}}{4\text{ ft}} \\ \\ \text{Flip the numerator and denominator on each side of the equation} \\ \frac{5\text{ in}}{y\text{ ft}}=\frac{1\text{ in}}{4\text{ ft}} \\ \frac{y\text{ ft}}{5\text{ in}}=\frac{4\text{ ft}}{1\text{ in}} \\ y\text{ ft }=\frac{5\text{ in}\cdot4\text{ ft}}{1\text{ in}} \\ y\text{ ft }=\frac{5\cancel{\text{ in}}\cdot4\text{ ft}}{1\cancel{\text{ in}}} \\ y\text{ ft }=20\text{ ft} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/tjqyg6e4vnjdxck0prbj3szunhisnty0p2.png)
Therefore, the length of the real boat is 20 feet.