A large cube is formed from the material obtained by melting three smaller cubes of 3, 4 and 5 cm side. What is the ratio of the total surface areas of the smaller cubes and the large cube?
2 : 1
3 : 2
25 : 18
27 : 20
Explanation:
Volume of the large cube = $(3^3 + 4^3 + 5^3) = 216 cm^3.$
Let the edge of the large cube be a.
So, $a^3 $= 216 a = 6 cm.
ஃ Required ratio = $(\dfrac{6 x (3^2 + 4^2 + 5^2)}{6 x 6^2}) = \dfrac{50}{36} $= 25 : 18
Volume of the large cube = $(3^3 + 4^3 + 5^3) = 216 cm^3.$
Let the edge of the large cube be a.
So, $a^3 $= 216 a = 6 cm.
ஃ Required ratio = $(\dfrac{6 x (3^2 + 4^2 + 5^2)}{6 x 6^2}) = \dfrac{50}{36} $= 25 : 18