Three cubes of sides 1 cm, 6 cm and 8 cm are melted to form a new cube. Find half of the surface area of the new cube.?

Q: Three cubes of sides 1 cm, 6 cm and 8 cm are melted to form a new cube. Find half of the surface area of the new cube.?

Volume (new cube) = (13 + 63 + 83 ) = 729 cm3 a3 = 729 ⇒ a = ∛ 729 ∴ Surface area of the new cube = 6a2 = 6 x 92 = 486 sq cm Surface area/2 = 486/2 = 243 sq cm

243 sq cm
463 sq cm
486 sq cm
293 sq cm

Correct Answer: 243 sq cm

Explanation:

Volume (new cube) = (1³ + 6³ + 8³ ) = 729 cm³
a³ = 729
⇒ a = ∛ 729
∴ Surface area of the new cube = 6a²
= 6 x 9² = 486 sq cm
Surface area/2 = 486/2 = 243 sq cm

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