Question

The decorative block shown in Fig. 13.7 is made of two solids - a cube and a hemisphere. The base of the block is a cube with edge 5 cm. and the hemisphere fixed on the top has a diameter of 4.2 cm. Find the total surface area of the block. $(Take\pi =\frac{22}{7})$

Answer 1

The total surface area is $=$ area of cube $+$ curved area of hemisphere $-$ base area of hemisphere

Area of the cube $A=6(a{)}^2=6(5{)}^2=150c{m}^2$

Curved area of hemisphere $B=2\pi r=$$2\pi \left(\frac{4.2}{2}\right)$$=27.72c{m}^2$

Base area of hemisphere $C=\pi r^2=\pi \frac{4.2}{2}=13.86c{m}^2$

Total surface area $=A+B-C=150+27.72-13.86=163.86c{m}^2$