Question

find the surface area of a sphere of diameter 21 cm with photo​

Answer 1

➣ Answer

• Surface area of sphere = 1386 cm².

➣ Given

• A sphere of diameter = 21 cm.

➣ To Find

• The surface area of the sphere.

➣ Step By Step Explanation

In this question we already know the diameter of sphere i.e. 21 cm. We need to find the surface area of the sphere. First we need to find the radius which will be half of the diameter i.e. 21/2. Then we will substitute the values in the formula.

So let's do it !!

➵ Formula Used

$\dag\underline{\boxed{ \tt{\color{purple}{Surface\:Area_{(Sphere)} = 4\pi\:{r}^{2}}}}}$

➵ By substituting the values

$\tt{Surface \: Area_{(Sphere)} = 4\pi { \bigg(\cfrac{21}{2} \bigg)}^{2}} \\ \\ \longmapsto \tt \cancel{4} \times \cfrac{22}{ \cancel7}\times \cfrac{ \cancel{21}}{\cancel2} \times\cfrac{21}{ \cancel2} \\ \\ \longmapsto \tt 22 \times 3 \times 21 \\ \\ \longmapsto{\tt{ \red{Surface \: Area_{(Sphere)} =1386 {cm}^{2}}}}$

Therefore, Surface area of sphere = 1386 cm².

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➣ More to Know

• Volume of sphere = $\tt\cfrac{4}{3}\pi{r}^{3}$ cubic units.

• Surface area of sphere = $\tt4\pi{r}^{2}$ sq. units.

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➣ Photo

$\setlength{\unitlength}{1.2cm}\begin{picture}(0,0)\thicklines\qbezier(2.3,0)(2.121,2.121)(0,2.3)\qbezier(-2.3,0)(-2.121,2.121)(0,2.3)\qbezier(-2.3,0)(-2.121,-2.121)(0,-2.3)\qbezier(2.3,0)(2.121,-2.121)(-0,-2.3)\qbezier(-2.3,0)(0,-1)(2.3,0)\qbezier(-2.3,0)(0,1)(2.3,0)\thinlines\qbezier (0,0)(0,0)(0.2,0.3)\qbezier (0.3,0.4)(0.3,0.4)(0.5,0.7)\qbezier (0.6,0.8)(0.6,0.8)(0.8,1.1)\qbezier (0.9,1.2)(0.9,1.2)(1.1,1.5)\qbezier (1.2,1.6)(1.2,1.6)(1.38,1.9)\put(0.2,1){\bf R}\end{picture}$

[ Note - Picture visible from brainly.in ]

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