If the pond is 15 feet wide, then adding 3 feet to each side would increase the side length to the square by six feet (3 feet on each side). This makes the area within the square equal to 18x18 feet, or 324 square feet. But, this isn’t the area of the sidewalk, it’s the area of the sidewalk plus the area of the pool.
The pool is fifteen feet wide, which means that it has an area of 225 square feet. So, to find the area of the side walk, we can subtract the area of the pool from the area of the pool and sidewalk, which will give us the area of the sidewalk by itself.
324-225=99 square feet.
The pool has an area of 225 square feet, and the sidewalk has an area of 99 feet.
