Area Of Sphere

Chapter 13 Class 9 Surface Areas and Volumes
Concept wise

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### Transcript

Ex 13.4 , 7 The diameter of the moon is approximately one fourth of the diameter of the earth. Find the ratio of their surface areas. Let diameter of earth = x So, diameter of moon = π₯/4 Hence, Radius of earth = π₯/2 & Radius of moon = 1/2Γπ₯/4 = π₯/8 Ratio of their surface area = (ππ’πππππ ππππ ππ ππππ)/(ππ’πππππ ππππ ππππππ‘β) = (4π(πππππ’π  ππ ππππ)^2)/(4π(πππππ’π  ππ ππππ‘β)^2 ) = (πππππ’π  ππ ππππ)^2/(πππππ’π  ππ ππππ‘β)^2 = (π₯/8)^2/(π₯/2)^2 = (π₯^2/8^2 )/(π₯^2/2^2 ) = π₯^2/8^2 Γ 2^2/π₯^2 = π₯^2/64 Γ 4/π₯^2 = 1/16