Question

Three solid cubes of sides $1	ext{ cm}$, $6	ext{ cm}$ and $8	ext{ cm}$ are melted to form a new cube. Find the surface area of the cube so formed.

Accepted Answer

B. Total volume $= 1^3 + 6^3 + 8^3 = 1 + 216 + 512 = 729	ext{ cm}^3$. Side of new cube $a = \sqrt[3]{729} = 9	ext{ cm}$. Surface area $= 6a^2 = 6 	imes 9^2 = 6 	imes 81 = 486	ext{ cm}^2$.

Surface area of combined cube

Explanation

Practise this under exam conditions