Question

find the area of circular ring ,if external and internal radii are 20cm and 6cm respectively

Answer 1

The area between the two concentric circular rings
is known as the area of Annulus.
Radius of the outer ring ( R ) = 20 cm
Radius of the inner ring ( r ) = 6 cm

Area of the annulus = Area of outer ring - Area of the inner ring

$Area = \pi R^{2} - \pi r^{2}$

$= \pi ( R^{2} - r^{2})$
[tex]= \frac{22}{7} * ( 20^{2} - 6^{2} ) [/tex]
[tex]= \frac{22}{7} * ( 400 - 36 ) [/tex]
= 22/7 * 364
= 22 *  52
= 1144 cm²

∴ The area between the two rings is 1144 cm².

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