Q.

The diameter of the moon is approximately one fourth of the diameter of the earth. The ratio of their surface areas is ____.


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Detailed Solution

Concept-
We are aware that the sphere's surface area is 4 πr2. The radius of a sphere is r.
Let earth's diameter equal x.
The moon's diameter is one-fourth that of the earth's.
So, moon diameter =x4 
So, to calculate radius:
earth's radius Equals x2
Moon's radius is 12×x4, or x8.
Now, their surface area ratio equals moon surface area to earth surface area.
 is being cancelled from both the numerator and the denominator. We obtain: =(Moon Radius)*2(Radius of earth)*2
 Substituting the moon's and the earth's radius. We obtain = (x8)2(x2)2 If you apply the denominator term to the numerator, you get =x282×22x2 =464.
By eliminating the x2 term, we arrive at the result: = 464 (Simple division) = 116.
Therefore, the moon's surface area to that of the earth is 1:16.
The right response is thus 1:16.
 
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