Find the area $ A $ of a pyramid if side $a = 40$ and slant height $s = 21$.

$A = 3280$

STEP 1: find base area $ B $

To find base area $ B $ use formula:

$$ B = a^2 $$

After substituting $ a = 40 $ we have:

$$ B = 40^2 $$ $$ B = 1600 $$

STEP 2: find lateral surface $ L $

To find lateral surface $ L $ use formula:

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

After substituting $ a = 40 $ and $ s = 21 $ we have:

$$ L = 80 \cdot 21 $$$$ L = 1680 $$

STEP 3: find total surface $ A $

To find total surface $ A $ use formula:

$$ A = B + L $$

After substituting $ B = 1600 $ and $ L = 1680 $ we have:

$$ A = 1600 + 1680 $$ $$ A = 1600 + 1680 $$ $$ A = 3280 $$

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