We have a square garden of 400 square foot.
The area of a square is:
![A=x^2](https://img.qammunity.org/2023/formulas/mathematics/college/x1y4r4sww1mkt75xuevlau09gk7r43gylu.png)
where x: side length.
In this case:
![\begin{gathered} A=400=x^2 \\ x=\sqrt[]{400}=20\text{ ft} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/tx545uujjptkzc416w551h6lx4pmw4ygh5.png)
The perimeter of the square is the sum of the lengths of the sides of the square. As they are all equal, we can write:
![P=4x=4\cdot20=80\text{ ft}](https://img.qammunity.org/2023/formulas/mathematics/high-school/rnvt9i0kpuu2z8kn3kvi5k17a2bx6ovayk.png)
The fencing is priced at $1.50 per foot. If we add the 7% sales tax to this price we get:
![C=1.50\cdot(1+0.07)=1.50\cdot1.07=1.605\text{ \$/ft}](https://img.qammunity.org/2023/formulas/mathematics/high-school/gbxekud9s8ff4u0vrhoprj9b6cq1kbozzs.png)
The fencing will be installed in all the perimeter (80 ft).
We can calculate the total cost by multiplying the sales price ($1.605 per foot) and the perimeter (80 ft):
![F=C\cdot P=1.605\frac{\text{\$}}{\text{ft}}\cdot80\text{ ft}=\$128.40](https://img.qammunity.org/2023/formulas/mathematics/high-school/h20ifr42zlp1p9ztac2jv9lbwldvjmh5up.png)
Answer: the fencing will cost a total of $128.40