In order to estimate the size of the crowd, let's find the area of the parade route.
The length is 3 miles, that is, 3 * 5280 = 15840 ft.
The width is 2 times 21, so 42 ft.
Therefore the area is:
[tex]A=15840\cdot42=665280[/tex]Now, to estimate the size of the crowd, let's use a rule of three, knowing that the area for 17 people is 7 * 7 = 49 ft²:
[tex]\begin{gathered} 17\text{ people}\to49\text{ ft}^2 \\ x\text{ people}\to665280\text{ ft}^2 \\ \\ \frac{17}{x}=\frac{49}{665280} \\ x=\frac{665280\cdot17}{49} \\ x=230811.43 \end{gathered}[/tex]Rounding to the nearest integer, we have 230,881 people.
