The volume of a certain rectangular solid is 8 cm^3. Its total surface area is 32 cm^2 and its three dimensions are in geometric progression. -Maths 9th

1 Answer

Answer :

(b) 32 Let the edges of the solid be a, ar, ar2. Then,  Volume = a x ar x ar2 = a3r3 = (ar)3.  Given (ar)3 = 8 ⇒ ar = 2  Also, surface area = 2(a x ar + ar x ar2 + a × ar2)  = 2(a2r + a2r3 + a2r2)  = 2ar (a + ar + ar2)  Given, 2ar (a + ar + ar2) = 32  ⇒ 4(a + ar + ar2) = 32  ; Sum of lengths of all edges = 32.

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