Three solid iron cubes of edges 4 cm, 5 cm and 6 cm are

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Three solid iron cubes of edges 4 cm, 5 cm and 6 cm are melted together to make a new cube. 62 cm² of the melted material is lost due to improper handling. The area (in cm²) of the whole surface of the newly formed cube is

1. 294
2. 343
3. 125
4. 216

Correct Option: A

Volume of all three cubes = (4² + 5² + 6²) cu.cm.
= (64 + 125 + 216) cu.cm. = 405 cu.cm.
∴ Volume of new cube = 405 – 62 = 343 cu.cm.
∴ Edge of cube = ³√343 = 7 cm.
∴ Surface area = 6 × 7² = 294 sq. cm.