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Area of Circular Rings (Annuli) - Class IX

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Find the area of a ring whose outer and inner radii are $19\ cm$ and $16\ cm$ respectively.

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A
$330\ cm^2$
💡 Explanation:

Area of outer circle $=\pi{(19)}^2$
                                 $=\cfrac{22}{7}\times 361$
Area of inner circle $=\pi{(16)}^2$
                                 $=\cfrac{22}{7}\times 256$
$\therefore$ area of the ring $=\dfrac{22}{7}\times 361-\dfrac{22}{7}\times 256$
                              $=\cfrac{22}{7}(361-256)$
                              $=\cfrac{22}{7}(105)$
                              $=330\ cm^2$

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