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# Diameter of a sphere is 21 dm. Find its surface area.A. 1386 $d{{m}^{2}}$B. 1376 $d{{m}^{2}}$C. 1356 $d{{m}^{2}}$D. 1380 $d{{m}^{2}}$

Last updated date: 11th Aug 2024
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Hint: In this problem, we have to find the surface area with the given diameter. We know that the diameter is equal to half radius. We also know the formula for the surface area of the sphere, to find the surface area, we need to find the radius form the given diameter. We can substitute the radius in the surface area formula and the value if pi, to get the required answer.

We know that the formula of surface area of sphere is,
$4\pi {{r}^{2}}$ …… (1)
We also know that the given diameter is 21 dm.
We can now find the radius of the sphere.
We know that the radius is half of the diameter.
Radius = $\dfrac{diameter}{2}$.
We can substitute the given value of diameter, we get
Radius = $\dfrac{21}{2}$
We also know that $\pi =\dfrac{22}{7}$, we can now substitute the pi value and the radius value in the formula (1), we get
Surface area of sphere = $4\times \left( \dfrac{22}{7} \right)\times {{\left( 10.5 \right)}^{2}}=1386d{{m}^{2}}$.