Question

what is the surface area?
11 mm
39 mm
11 mm
square millimeters
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Explanation:

Step1: Recall surface area formula

The surface area $SA$ of a rectangular prism is $SA=2(lw + lh + wh)$, where $l=39$, $w=11$, $h=11$.

Step2: Calculate each face area sum

First compute $lw + lh + wh$:

$$\begin{align*} lw + lh + wh&=(39\times11)+(39\times11)+(11\times11)\\ &=429+429+121\\ &=979 \end{align*}$$

Step3: Multiply by 2 for total surface area

$SA=2\times979$

Answer:

2158 square millimeters