Question

If the area of a circular card board is 154 Cm2 , then its circumference (in form of pie) is ________.

(a) 14π Cm.


( b) 7π Cm .


(c) 21πCm.


(d)28 π Cm.
​

Answer 1

Given :

• Area of Circular Card Board is 154 cm².

To Find :

• Circumference of Base in the form of π .

Solution :

Firstly we will Find the Radius of Board :

Using Formula :

$\longmapsto\tt\boxed{Area\:of\:Circle=\pi{{r}^{2}}}$

Putting Values :

$\longmapsto\tt{154=\dfrac{22}{7}\times{{r}^{2}}}$

$\longmapsto\tt{154\times{7}=22\times{{r}^{2}}}$

$\longmapsto\tt{1078=22\:{r}^{2}}$

$\longmapsto\tt{\cancel\dfrac{1078}{22}={r}^{2}}$

$\longmapsto\tt{\sqrt{49}=r}$

$\longmapsto\tt\bf{7\:cm=r}$

Radius of Circular Card Board is 7 cm .

Now ,

$\longmapsto\tt{Radius=7\:cm}$

Using Formula :

$\longmapsto\tt\boxed{Circumference\:of\:Circle=2\pi{r}}$

Putting Values :

$\longmapsto\tt{2\times{\pi\times{7}}}$

$\longmapsto\tt\bf{14\:\pi\:cm}$

So , The Circumference of Circular Card board is 14 π cm

Option a)14 π cm is Correct ..

Answer 2

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If the area of a circular card board is 154 Cm2 , then its circumference (in form of pie) is ________.

$\huge {\underline {\mathfrak{ \red g \blue i\green \pink v\orange e\purple n\red \: - }}}$

Area =154cm^2

$\large\dag \ {{\boxed {\pink{\rm{formula \: used\: \ \: }}}}}$

$\dag \ {{\boxed {\ \: {\rm{ \bf area \: of \: a \: circle = \pi {r}^{2} \: \: \ \: }}}}}†† </p><p>$

$\dag \ {{\boxed {\ \: {\rm{ \bf circumferenc \: of \: a \: circle= 2 \pi r \: \: \ \: }}}}}†† </strong><strong>\</strong><strong>\</strong><strong>\</strong><strong>\</strong><strong>\</strong><strong>\</strong><strong> </strong></p><p></p><p>\huge {\underline {\mathfrak{ \red a \blue n \green \pink s \orange w\purple e\red r\: - }}}$

☞Area of the circle = πr^2

☞154 =22/7 × r^2

☞(154 ×7)/22 =r^2

☞ r = √49

☞ r = 7

__________________

个After that个

$\large\dag \ {{\boxed {{\rm{ \: Circumference \: of \: the \: circle\: in \: the \: from \: of \:\pi: }}}}}$

☞ Circumference of the circle=2πr=2× π ×7

☞ =14π

^