Example problem of a hemisphere — lesson. Mathematics CBSE, Class 9.

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The diameter of an orange is

$8 \ cm$ . Calculate the total surface area of the half orange.

Solution:

Diameter of an orange

$(d)$

$=$

$8 \ cm$

Radius of an orange

$(r)$

$=$

$\frac{d}{2} = \frac{8}{2} = 4 cm$

A half orange is in the shape of a hemisphere.

Total surface area of a hemisphere

$=$

$3 \pi r^2$ sq. units

$=$

$3 \times \frac{22}{7} \times 4^{2}$

$=$

$3 \times \frac{22}{7} \times 16$

$=$

$150.86$

Total surface area of the half orange is

$150.86 \ cm^2$ .

Important!

The value of

$\pi$ should be taken as

$\frac{22}{7}$ unless its value is shared in the problem.

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4. Example problem of a hemisphere