Discussion

If a cuboid is 3.2 cm high, 8.9cm long and 4.7 wide then total surface area is

Answer: A

A cuboid has three pairs of identical faces.

\[ \text{TSA} = 2(lb + bh + hl) \]

\[ = 2\left(8.9 \times 4.7 + 4.7 \times 3.2 + 3.2 \times 8.9\right) \]

\[ = 2(41.83 + 15.04 + 28.48) = 2(85.35) \]

\[ = 170.7 \text{ cm}^{2} \]

Each of the three products must appear twice; summing them once gives 85.35, exactly half the answer.

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