Find the area $ A $ of a pyramid if slant height $s = 10$ and base area $B = 81$.

$A = 261$

STEP 1: find side $ a $

To find side $ a $ use formula:

After substituting $ B = 81 $ we have:

$$ B = a^2 $$ $$ a^2 = 81 $$ $$ a = \sqrt{ 81 } $$ $$ a = 9 $$

STEP 2: find lateral surface $ L $

To find lateral surface $ L $ use formula:

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

After substituting $ a = 9 $ and $ s = 10 $ we have:

$$ L = 18 \cdot 10 $$$$ L = 180 $$

STEP 3: find total surface $ A $

To find total surface $ A $ use formula:

$$ A = B + L $$

After substituting $ B = 81 $ and $ L = 180 $ we have:

$$ A = 81 + 180 $$ $$ A = 81 + 180 $$ $$ A = 261 $$

Pyramid Calculator