Given that diameter is equal to height of a cylinder
So, h = 2r
Diameter = 42cm
Height = 21cm
Diameter (d) = 2r
2r = 42
r = 21
Radius = 21cm
Volume of vessel = π(21)2 x 21 ..........(2)
Since volumes are equal
Equating (1) and (2)
Radius of cylindrical vessel = 21cm
Diameter of cylindrical vessel = 42cm.