Explanation
Given, radius r=2.8 cm.
We know that, the surface area of a sphere of radius r =4πr2
=4×227×2.8×2.8
=98.56cm2.
Let radius of sphere be r cm.
We know, surface area of sphere =4πr2
⟹ 221.76cm2=4πr2
⟹ r2=221.764π=221.76×74×22=17.64
⟹ r=√17.64=4.2cm .
Then, diameter of the sphere, d=2r=2×4.2=8.4cm.
Therefore, option A is correct.
The formula for calculating the surface area of a cuboid of dimensions :
l×b×h is :
2×(l×b+b×h+h×l)
Substituting,
l=10cm
b=4cm
h=3cm
Surface area = 2×(10×4+4×3+3×10)
=2×(40+12+30)
=2×82cm2
=164cm2
Hence, the answer is option (C)
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