Question

Calculate the circumference of circles with a given radius/diameter. a- r = 7.5cm b- d = 5cm

Answer 1

Question:-

➙Calculate the circumference of circles with a given radius or diameter.

➙a) r=7.5cm

➙b) d= 5cm

Answer:-

we know that:-

➙formula of circumference of a circle is= 2×pi×r

a) r=7.5cm (given)

So the circumference is= 2×pi×r

= (2×pi×7.5)cm.

and we know that pi= 3.14cm.

so, circumference= (2×3.14×7.5)cm.

=47.1cm.

b) d=5cm (given).

So r=2.5cm.

so the circumference is=2×pi×r.

= (2×3.14×2.5)cm.

= 15.7cm.

or you can write

circumference of the circle whose diameter is 5= pi×d

= (3.14×5)cm

= 15.7cm

➙formula used for finding circumference of a circle is

➙a) 2×pi×r (when radius is given)

➙b) pi×d(when diameter is given)

hope this helps uh ♡~

Answer 2

★ Appropriate Question ★

Calculate the circumference of circles with a given radius/diameter.

a) r = 7.5cm

b) d= 5cm

★ Required Solution ★

• $\boxed {\large \bf { a) \: r = 7.5cm } }$

Given:

• $\sf { Radius = 7.5cm }$

To calculate:

• $\sf { Circumference }$

Calculation:

We know that,

• $\boxed {\huge \bf \gray { C=2πr } }$

[ Value of π is $\sf{ \dfrac{ 22}{7} }$ ]

$\sf { \implies C = 2 \times \dfrac{ 22}{7} \times 7.5 }$

$\sf { \implies C = \cancel{2} \times \dfrac{ 22}{7} \times \dfrac{ 75}{\cancel{10}} }$

$\sf { \implies C = \dfrac{ 22}{7} \times \cancel{\dfrac{75}{5}} }$

$\sf { \implies C = \dfrac{ 22}{7} \times 15 }$

$\sf { \implies C = \dfrac{ 22 \times 15 }{7} }$

$\sf { \implies C = \dfrac{ 330 }{7} }$

$\boxed {\large \bf \red { C=47.14 cm} }$

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• $\boxed {\large \bf { b) \: d= 5cm } }$

Given:

• $\sf { Diameter = 5cm }$

Since D = 2r

So, Radius = D/2

=$\sf { \dfrac{ 5}{2}}$

To calculate:

• $\sf { Circumference }$

Calculation:

We know that,

• $\boxed {\huge \bf \gray { C=2πr } }$

[ Value of π is $\sf{ \dfrac{ 22}{7} }$ ]

$\sf { \implies C = \cancel{2} \times \dfrac{ 22}{7} \times \dfrac{5}{\cancel{2}} }$

$\sf { \implies C = \dfrac{ 22}{7} \times 5 }$

$\sf { \implies C = \dfrac{ 22 \times 5 }{7} }$

$\sf { \implies C = \dfrac{ 22 \times 5 }{7} }$

$\sf { \implies C = \dfrac{ 110 }{7} }$

$\boxed {\large \bf \red { C=15.71 cm} }$

$\sf \blue { So, we \: are \: done!! }$

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★ Extra Shots!!

• Circumference of the circle is also called perimeter of the circle.

• Circumference of the circle = 2πr

• Diameter of the circle = 2 × radius

• Value of the π is 22/7 or 3.14.

• Area of the circle = $\sf { π{r}^{2} }$

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