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Four eqal circles are described at …

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Four eqal circles are described at the four corners of a circle so that each touches two of the others .The shaded area enclosed between the circles is 24/7sq.cm .Find the radius.
  • 1 answers

Sia ? 6 years, 4 months ago


Let {tex}r {/tex} cm be the radius of each circle.
Area of square - Area of 4 sectors = {tex}\frac { 24 } { 7 } \mathrm { cm } ^ { 2 }{/tex}
(side)2 -  {tex}4\left[\frac\theta{360}\mathrm{πr}^2\right]{/tex} = {tex}\frac { 24 } { 7 } \mathrm { cm } ^ { 2 }{/tex}
or, {tex}( 2 r ) ^ { 2 } - 4 \left( \frac { 90 ^ { \circ } } { 360 ^ { \circ } } \times \pi r ^ { 2 } \right) = \frac { 24 } { 7 }{/tex}
or, {tex}( 2 r ) ^ { 2 } - 4 \left( \frac { 1 } { 4 ^ { \circ } } \times \pi r ^ { 2 } \right) = \frac { 24 } { 7 }{/tex}
or, {tex}( 2 r ) ^ { 2 } - \left( \pi r ^ { 2 } \right) = \frac { 24 } { 7 }{/tex}
or, {tex}4 r ^ { 2 } - \frac { 22 } { 7 } r ^ { 2 } = \frac { 24 } { 7 }{/tex}
or, {tex}\frac { 28 r ^ { 2 } - 22 r ^ { 2 } } { 7 } = \frac { 24 } { 7 }{/tex}
or, {tex}6r^2 = 24{/tex}
or, {tex}r^2 = 4{/tex}
or, {tex}r = \pm 2{/tex}
or, Radius of each circle is 2 cm (r cannot be negative)

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