Answer:
221 students were enrolled when the school was first opened.
Explanation:
Area of the school while opened up new = 4800 square feet
At the time of opening population density of the school was = 0.046 students per square feet.
That means total number of students at the time of opening = Area of the school × population density
= 4800 × 0.046
= 220.80
≈ 221 students
If 176 new students were enrolled then total number of students enrolled since the opening = 221 + 176 = 397 students
Now population density =

Which is less than 0.1 students per square feet.
The principal of the school determined that the new school building will be built if the population density reaches to 0.1 students per feet².
Therefore, the new building will not be required.