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# A right circular cylinder just encloses a sphere of radius r (see fig. 13.22). Find (i) surface area of the sphere, (ii) curved surface area of the cylinder, (iii) ratio of the areas obtained in(i) and (ii). Q.9

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What is the best way for solving the question from class 9th ncert math of Surface areas and Volumes chapter of Ncert of exercise 13.4    of math. What is the best way for solving this question please guide me the best way for solving this question. A right circular cylinder just encloses a sphere of radius r (see fig. 13.22). Find (i) surface area of the sphere, (ii) curved surface area of the cylinder, (iii) ratio of the areas obtained in(i) and (ii).

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1. (i) Surface area of sphere = 4πr2, where r is the radius of sphere

(ii) Height of cylinder, h = r+r =2r

CSA of cylinder formula = 2πrh = 2πr(2r) (using value of h)

= 4πr2

(iii) Ratio between areas = (Surface area of sphere)/CSA of Cylinder)

= 4r2/4r2 = 1/1

Ratio of the areas obtained in (i) and (ii) is 1:1.

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