Known :
Sa = 28.26 ft
Asked :
d = ...?
Answer :
Sa = 4πr²
28.26 = 4 × 3.14 × r²
28.26 = 12.56 r²
r² = 28.26 ÷ 12.56
r² = 2.25
r = √2.25
r = 1.5 ft
diameter = 2 × radius = 2 × 1.5 = 3 ft
So, the diameter is 3 ft (2nd choice)
Hope it helpful and useful :)
