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Mathematics

The area of a circle is 394.24 cm2. Calculate :

(i) the radius of the circle,

(ii) the circumference of the circle.

Mensuration

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Answer

(i) Let the radius of circle be r cm.

Given,

Area = 394.24 cm2

Area of circle = πr2

⇒ 394.24 = 227\dfrac{22}{7} × r2

⇒ r2 = 394.24×722\dfrac{394.24 × 7}{22}

⇒ r2 = 125.44

⇒ r = 125.44\sqrt{125.44}

⇒ r = 11.2 cm.

Hence, radius = 11.2 cm.

(ii) Circumference of circle = 2πr

= 2 × 227\dfrac{22}{7} × 11.2

= 2 × 22 × 1.6

= 70.4 cm.

Hence, circumference = 70.4 cm.

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