3.
Find the area of the circle whose diameter is:
(Taken=)
22/7
(i) 14 cm
(ii) 56 cm
(iii) 63 dm
(iv) 84 dm
Answers
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Question :
Find the area of the circle whose diameter is:
(i) 14 cm
(ii) 56 cm
(iii) 63 dm
(iv) 84 dm
Solution :
(i) 14 cm
Area of circle = πr^2
=> r = d/2
=> r = 14/2
=> r = 7 cm
=> 22/7 × (7 cm)^2
=> 22/7 × 7 × 7 cm^2
=> 22 × 7 cm^2
=> 154 cm^2
(ii) 56 cm
Area of circle = πr^2
=> r = d/2
=> r = 56/2
=> r = 28 cm
=> 22/7 × (28 cm)^2
=> 22/7 × 28 × 28 cm^2
=> 22 × 28 × 4 cm^2
=> 2464 cm^2
(iii) 63 dm
Area of circle = πr^2
=> dm = 10 cm
=> 63 dm = 63 × 10 cm
=> 630 cm
=> r = d/2
=> r = 630/2
=> r = 315 cm
=> 22/7 × (315 cm)^2
=> 22/7 × 315 × 315 cm^2
=> 22 × 315 × 45 cm^2
=> 311850 cm^2
(iv) 84 dm
Area of circle = πr^2
=> dm = 10 cm
=> 84 dm = 84 × 10 cm
=> 840 cm
=> r = d/2
=> r = 840/2
=> r = 420 cm
=> 22/7 × (420 cm)^2
=> 22/7 × 420 × 420 cm^2
=> 22 × 420 × 60 cm^2
=> 554400 cm^2
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