First a integer is a hole number not a fraction it is 2080
What are the options? could you type it out a little more clear if possible? thanks!
Answer:
The area of the circular cross section of the pipe is 
Step-by-step explanation:
we know that
The area of the circle (cross section of the pipe) is equal to

we have
----> the radius is half the diameter
substitute


50
0+99
1+98
....
....
49+50
Then stop
because 49+50 is the same pair as 50+49 and 51+48 is the same as 48+51 (already counted)