Answer :

(1). We have been given: radius = 42 cm


We need to find: diameter = ?, circumference = ? and area = ?


We have



To find diameter:


Diameter = 2 × radius


diameter = 2 × 42 = 84 cm


To find circumference:


Circumference = 2πr, where r = radius


Circumference


Circumference


To find area:


Area = πr2, where r = radius


Area


Area


Thus, diameter = 84 cm, circumference = 264 cm & area = 5544 cm2.


(2). Given: diameter = 9.8 m


We need to find: radius = ?, circumference = ? & area = ?


We have



To find radius:


Radius = diameter/2


radius = 9.8/2 = 4.9 m


To find circumference:


Circumference = 2πr, where r = radius


Circumference


Circumference


To find area:


Area = πr2, where r = radius


Area


Area


Thus, diameter = 4.9 m, circumference = 30.8 m & area = 75.46 m2.


(3). Given: circumference = 44 m


We need to find: radius = ?, diameter = ? & area = ?


To find radius:


If circumference = 44 m


2πr = 44 [, circumference of circle = 2πr, where r = radius]





radius = 7 m …(i)


To find diameter:


Diameter = 2 × radius


diameter = 2 × 7 = 14 m [from (i)]


To find area:


Area = πr2


[from (i)]


Area = 22 × 7 = 154 m2


Thus, radius = 7 m, diameter = 14 m & area = 154 m2.


(4). Given: area = 616 cm2


We need to find: radius = ?, diameter = ? & circumference = ?


To find radius:


If area = 616 cm2


πr2 = 616 [, area of circle = πr2, where r = radius]





r = √196 = 14 cm …(i)


To find diameter:


Diameter = 2 × radius


diameter = 2 × 14 = 28 cm


To find circumference:


Circumference = 2πr, where r = radius


Circumference


Circumference


Thus, radius = 14 cm, diameter = 28 cm and circumference = 88 cm.


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