Q. 15.0( 1 Vote )

# Write the proper

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 = πr^{2}, where r = radius

⇒ Area

⇒ Area

Thus, diameter = 84 cm, circumference = 264 cm & area = 5544 cm^{2}.

(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 = πr^{2}, where r = radius

⇒ Area

⇒ Area

Thus, diameter = 4.9 m, circumference = 30.8 m & area = 75.46 m^{2}.

(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 = πr^{2}

⇒ [from (i)]

⇒ Area = 22 × 7 = 154 m^{2}

Thus, radius = 7 m, diameter = 14 m & area = 154 m^{2}.

(4). Given: area = 616 cm^{2}

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

To find radius:

If area = 616 cm^{2}

⇒ πr^{2} = 616 [∵, area of circle = πr^{2}, 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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