2 stands for square.

Outer diameter: 30× 1/5 ÷ 2 = 3 (cm)

Inner diameter: 3-1÷ 2 = 2.5cm.

Tube area: 3.14× 3 2-3.14× 2.5 2 = 8.635 (square centimeter).

Tube volume: 8.635× 30 = 259.05 (cubic centimeter)

Weight of steel pipe: 259.05× 7.8 = 2020.59 (g) = 2.02059 (kg)