She is in 6th grade. there are 52 weeks in a year, and 146/52 is approximately equal to 2.8. If she was starting 4th grade in the beginning of the year, then she would now be nearing the end of 6th grade.
Smaller circle:
diameter = 9 ft
radius = diameter/2 = (9 ft)/2 = 4.5 ft
A = pi(r^2) = 3.14159 * (4.5 ft)^2 = 63.62 ft^2
Larger circle:
diameter = 20 ft
radius = diameter/2 = (20 ft)/2 = 10 ft
A = pi(r^2) = 3.14159 * (10 ft)^2 = 314.159 ft^2
Difference = larger are - smaller area
Difference = 314.16 ft^2 - 63.62 ft^2 = 250.54 ft^2
Answer: About 251 ft^2