Find the area $ A $ of a pyramid if side $a = 4$ and slant height $s = 21$.

$A = 184$

STEP 1: find base area $ B $

To find base area $ B $ use formula:

$$ B = a^2 $$

After substituting $ a = 4 $ we have:

$$ B = 4^2 $$ $$ B = 16 $$

STEP 2: find lateral surface $ L $

To find lateral surface $ L $ use formula:

$$ L = 2 \cdot a \cdot s $$

After substituting $ a = 4 $ and $ s = 21 $ we have:

$$ L = 8 \cdot 21 $$$$ L = 168 $$

STEP 3: find total surface $ A $

To find total surface $ A $ use formula:

$$ A = B + L $$

After substituting $ B = 16 $ and $ L = 168 $ we have:

$$ A = 16 + 168 $$ $$ A = 16 + 168 $$ $$ A = 184 $$

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