Find the total surface area of a hollow hemisphere whose outer and inner radii are $4.2 cm$ and $2.1 cm$ respectively.

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Solution

Total Surface Area of a Hemisphere is equal to $2 π r^{2}$ .

Given $\Rightarrow$ Outer radii $(r_{1}) = 4.2 cm$
Inner radii $(r_{2}) = 2.1 cm$

Total Surface area of a hollow hemisphere,
$\Rightarrow 2 π ({r_{1}}^{2} - {r_{2}}^{2}) + π (r_{1}^{2} - r_{2}^{2})$
$\Rightarrow 3 \times \frac{22}{7} ({4.2}^{2} - {2.1}^{2})$
$\Rightarrow \frac{66}{7} (4.2 - 2.1) (4.2 + 2.1)$
$\Rightarrow \frac{66}{7} \times 2.1 \times 6.3$
$\Rightarrow 124.74 sq. cm$

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Find the total surface area of a hollow hemisphere whose outer and inner radii are 4.2 cm and 2.1 cm respectively.

Total Surface Area of a Hemisphere is equal to 2πr2.Given ⇒ Outer radii (r1)=4.2 cm Inner radii (r2)=2.1 cmTotal Surface area of a hollow hemisphere,⇒2π(r12−r22)+π(r21−r22)⇒3×227(4.22−2.12)⇒667(4.2−2.1)(4.2+2.1)⇒667×2.1×6.3⇒124.74 sq. cm

Find the total surface area of a hollow hemisphere whose outer and inner radii are $4.2 cm$ and $2.1 cm$ respectively.