To find area $ A $ use formula:
$$ A = \dfrac{ 3 \sqrt{ 3 } \cdot a^2 }{ 2 } $$After substituting $ a = 100 $ we have:
$$ A = \dfrac{ 3 \sqrt{ 3 } \cdot 100^2 }{ 2 } $$ $$ A = \dfrac{ 3 \sqrt{ 3 } \cdot 10000 }{ 2 }$$ $$ A = \dfrac{ 30000 \sqrt{ 3 } }{ 2 }$$ $$ A = 15000 \sqrt{ 3 } $$