Question

please give the answer for following question...​

Answer 1

Step-by-step explanation:

Given :-

a) Radius = 21 cm

b) Diameter = 35 cm

c) Circumference = 484 cm

To find :-

Area of the following circles ?

Solution :-

a)

Given that

Radius of the circle (r) = 21 cm

We know that

Area of a circle whose radius is r units is

πr² sq.units

Area of the given circle

=> A = (22/7)×21² cm²

=> A = (22/7)×21×21 cm²

=> A = 22×3×21 cm²

=> A = 1386 cm²

Area of the circle = 1386 cm²

b)

Given that

Diameter of the circle (d) = 35 cm

Radius = Diameter/2

=> Radius = 35/2 cm

Area of a circle whose radius is r units is

πr² sq.units

Area of the given circle

=> A = (22/7)×(35/2)² cm²

=> A = (22/7)×(35/2)×(35/2) cm²

=> A = (22×35×35)/(7×2×2) cm²

=> A = 11×35×5/2 cm²

=> A = 1925/2 cm²

=> A = 962.5 cm²

Area of the circle = 962.5 cm²

(or)

Diameter of the circle (d) = 35 cm

We know that

Area of a circle whose diameter is d units is πd²/4 sq.units

Area of the given circle

=> A = (22/7)×(35)²/4 cm²

=> A = (22/7)×(1225/4) cm²

=> A = (22×1225)/(4×7) cm²

=> A = (11×175)/2 cm²

=> A = 1925/2 cm²

=> A = 962.5 cm²

Area of the circle = 962.5 cm²

(c)

Given that

Circumference of the circle (C) = 484 cm

We know that

Circumference of a circle whose radius is r units is 2πr units

=> 2πr = 484

=> 2×(22/7)×r = 484

=> (44/7)×r = 484

=> r = 484×(7/44)

=> r = 11×7

=> r = 77 cm

Area of a circle whose radius is r units is

πr² sq.units

Area of the given circle

=> A = (22/7)×(77)² cm²

=> A = (22/7)×77×77 cm²

=> A = (22×77×77)/7 cm²

=> A = 22×77×11 cm²

=> A = 18634 cm²

Area of the circle = 18634 cm²

(or)

Circumference of the circle (C) = 484 cm

We know that

Area of a circle whose circumference is C units is C²/4π units

Area of the circle

=> A = (484)²/[4×(22/7)]

=> A = (484×484)/(88/7)

=> A = (484×484)×(7/88)

=> A = 1639792/88

=> A = 18634 cm²

Area of the circle = 18634 cm²

Answer:-

a) Area of the circle = 1386 cm²

b) Area of the circle = 962.5 cm²

c) Area of the circle = 18634 cm²

Used formulae:-

→Area of a circle whose radius is r units is

πr² sq.units

→Area of a circle whose diameter is d units is πd²/4 sq.units

→ Circumference of a circle whose radius is r units is 2πr units

→ Area of a circle whose circumference is C units is C²/4π units

• r = radius
• π = 22/7
• C = Circumference
• d = diameter
• A = Area

Answer 2

Given :

$\rm(a).\: Radius = 21 cm$

$\rm(b). \:Diameter = 35 cm$

To Find :

$\rm \implies \: Area \: of \: circle \:$

Note :

$\rm\implies \: Take \: the \: value \: of \: \pi =\dfrac{22}{7}$

Formula used :

$\rm \implies \: Area \: of \: circle = \pi {r}^{2}$

$\rm \implies \: Radius \: of \: circle = \dfrac{Diameter }{2}$

Solution :

$\rm(a).\: Radius = 21 cm$

$\rm\: By \: using \: formula \: of \: area \: of \: circle \: ,$

$\rm \implies \: Area \: of \: circle = \pi {r}^{2}$

$\rm \: Now \: Place \: value \: of \: r \: and \: \pi\: in \: given \: formula$

$\rm \implies \: Area \: of \: circle = \dfrac{22}{7} \times {21}^{2}$

$\rm \implies \: \dfrac{22}{7} \times 21 \times 21$

$\rm \implies \: 22 \times 3 \times 21$

$\rm \implies \: 66\times 21$

Therefore ,

$\rm \therefore \: Area \: of \: circle =1386 \: cm \: square$

==========================

$\rm(b). \:Diameter = 35 cm$

$\rm\: By \: using \: formula \: of \: finding\: radius\: ,$

$\rm \implies \: Radius \: of \: circle = \dfrac{Diameter }{2}$

$\rm \implies \: \dfrac{35}{2} = 17.5 \: cm$

$\rm \: Now \: by \: using \: formula \: of \: area \: of \: circle$

$\rm \implies \: Area \: of \: circle = \pi {r}^{2}$

$\rm \: Now \: Place \: value \: of \: r \: and \: \pi\: in \: given \: formula$

$\rm \implies \: Area \: of \: circle = \dfrac{22}{7} \times {(17.5)}^{2}$

$\rm \implies \: \dfrac{22}{7} \times 17.5 \times 17.5$

$\rm \implies \: 22 \times 2.5 \times 17.5$

$\rm \implies \:55 \times 17.5$

Therefore ,

$\rm \therefore \: Area \: of \: circle = 962.5\: cm \:square\:$

• Refer the attachment