direct an inverse variation
posted by Anonymous .
The number of books checked out from the library varies directly with the number of book reports assigned. There were 3375 books checked out when there were 225 book reports assigned.
How many book reports have been assigned if there are 13,500 books

c = checked out
r = reports
c = kr
3375 = k*225
k = 15

13500 = 15r
r = 900 
The area of a classroom space per student varies inversely with the number of students in the room. When there are 15 students in the room, each student has 20 sq ft of space.
How many square feet of space are available per student when there are 25 students in the classroom?
A. 60 sq ft
B. 33 sq ft
C. 12 sq ft
D. 20 sq ft