Question 1181626
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The diameter is 18 feet, so the radius is 9 feet.
The area of the whole circular garden is pi times the square of the radius.
The side of the square is 4 feet.
The area of the square is the square of the side length.
Subtract the area of the concrete slab from the area of the whole garden to get the area of grass.
Multiply the area of the grass (it is in square feet) times the cost per square foot of the grass.<br>
All easy calculations....  Do them.<br>