A closed box is built of wood of uniform thickness. Its external dimensions are 12 cm, 10 cm and 8 cm. If the inner surface area is 376 square cm, then what is the thickness of the wood?

Explanation

Let thickness be t. Inner dimensions are (12-2t), (10-2t), (8-2t). Inner surface area 2[(12-2t)(10-2t) + (10-2t)(8-2t) + (8-2t)(12-2t)] = 376. By substituting t=1, the dimensions become 10, 8, 6, and surface area is 2(80 + 48 + 60) = 2(188) = 376, which perfectly matches.

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