Volume of a cylinder = πr²h
1256 = (3.14) x (r)² x (13)
1256 = 40.82r²
r² = 1256 ÷ 40.82
r² = 30.769
r = √30.69
r = 5.547
Diameter = Radius x 2
Diameter = 5.547 x 2
Diameter = 11.09 units (nearest hundredth)
If you have 50. and want to make it 5000 you can move the decimals point over 2 which would also be ×100