Answer:
[tex]\begin{gathered} a)20m^2 \\ b)\text{ 20 bags of colored stones} \\ c)\text{ \$499.8} \end{gathered}[/tex]Step-by-step explanation:
Since the square fountain measures 4 meters on each side and the walkway will be one meter wide, let's make a diagram to see the situation:
Then, to calculate the area of the walkway (green shaded region)
[tex]\begin{gathered} A_{total}=b\cdot h \\ A_{total}=6\cdot6=36m^2 \\ A_{founta\in}=4\cdot4=16m^2 \end{gathered}[/tex][tex]\begin{gathered} A_{walkway}=A_{total}-A_{fountain} \\ A_{walkway}=36-16=20m^2 \end{gathered}[/tex]Now, how many colored stones will be needed if one bag covers 1 square meter:
There are 20 square meters on the walkway, then will be needed 20 bags of colored stones.
A bag of colored stones costs $24.99, then multiply 20 by $24.99:
[tex]20\cdot24.99=\text{ \$499.8}[/tex]