20 team members paint a 4800 square wall in 36 minutes.
How fast can one team member paint?
20 * 36 = 720 minutes
One team member can paint a 4800 square wall in 720 minutes.
How fast can one team member paint a square wall of 3600 square feet?
720 * (3600/4800) = 540 minutes
Now how fast would it take 9 team members?
540 / 9 = 60 minutes.
Which matches KIson!