The figure shows cross-section of a beam subjected to bending.

The figure shows cross-section of a beam subjected to bending. The area moment of inertia (in mm⁴) of this cross-section about its base is

I_base =I_{rect abt base} -2I _{semicircle abt base}
I =((I_C.G +AY²) -2(I_C.G +AY²)

=		bd₃	+ (bd)y²		- 2		π		d²	+		1	× πr²y²
		12					64		(2)			2

=		10 × 20³	+ 10 × 20 × 10²		- 2		π	×	8⁴	+	1	× π× 4² × 10²
		12					64		(2)		2

= 21439.06 mm⁴.