Question

A hemispherical bowl has its external diameter equal to 10 cm and its thickness is 1 cm. What is the whole surface area of the bowl ?

Answer 1

External radius of hemispherical bowl = 5 cm 

Internal radius of the bowl = (5 – 1) cm = 4 cm 

Surface area of external portion = 2π(5)² = 50 p sq. cm 

Surface area of internal portion = 2π(4)² = 32 p sq. cm 

Area of the top circular portion = π(5² – 4²) = 9p sq. cm 

∴ Total surface area of the bowl = 50π + 32π + 9π 

= 91π sq. cm = \(\big(91\times\frac{22}{7}\big)\) sq. cm 

= 13 × 22 sq. cm = 286 cm².