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In the figure, a circle is inscribed in a square of side 5 cm and another circle is circumscribing the square. Find the ratio of the area of the outer circle to that of the inner circle.

In the figure, a circle is inscribed in a square of side 5 cm and another circle is circumscribing the square. Find the ratio of the area of the outer circle to that of the inner circle. Circumference & Area of a Circle, R.S. Aggarwal Mathematics Solutions ICSE Class 9.

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Answer

Given,

Side of square = 5 cm.

Let A1 and A2 be the areas of the inner and outer circle respectively.

Inner circle (inscribed in the square):

Diameter of the circle = side of the square

Diameter = 5 cm

So, radius = 52\dfrac{5}{2} = 2.5 cm.

Area of inner circle (A1) = πr2

= π(2.5)2

= 6.25π cm2

Outer circle (circumscribing the square)

Diameter of the outer circle = Diagonal of the square

Diameter of the outer circle = a2=52a\sqrt{2} = 5\sqrt{2} cm.

Radius of the outer circle = 522\dfrac{5\sqrt{2}}{2}

Area of outer circle (A2) = πr2

= π(522)2π\Big(\dfrac{5\sqrt{2}}{2}\Big)^2

= π × 25×24\dfrac{25 × 2}{4}

= 12.5π cm2.

Ratio of areas :

Outer area : Inner area

A2 : A1

12.5π : 6.25π

2 : 1.

Hence, ratio = 2 : 1.

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