Answer:
Ā about 53.4 square feet more
Step-by-step explanation:
You want to know how much more space a circle with 9 ft radius has than a circle with 16 ft diameter.
Area
The formulas for area of a circle can be written as ...
Ā A = Ļr²
Ā A = (Ļ/4)d²
We can use these two formulas to find the difference in area between the larger and smaller circles.
Difference
Ā Ā tree II space - tree I space
Ā = Ļ(9 ft)² - Ļ/4(16 ft)² ā 53.4 ft²
Tree II requires about 53.4 square feet more space than tree I.
__
Additional comment
We could use the same formula twice by converting the diameter to a radius, or vice versa. We can also use the factoring of the difference of squares to change the way we do the computation:
Ā Ļ(9 ft)² -(Ļ/4)(16 ft)² = Ļ(9 ft -8 ft)(9 ft +8 ft) = 17Ļ ft² ā 53.4 ft²