1. 點解冇圖ge...................唔知道shaded area係咩wo = =

2.Let the height be h.
The volume of the metal cube = 10 x 10 x 10 = 1000cm3
The volume of one cylinder = (1^2) π h =  π h
The volume of 20 cylinder = 20πh

The volume of 20 cylinder = The volume of the metal cube
20πh = 1000
h = 50 / π = 15.9 (to 3 significant figure)

3. 唔識，因為唔知兩個cylinder的height
(可能計到ge，不過我笨，唔識= =)