STEP 1: find radius $ r $
To find radius $ r $ use formula:
$$ d = 2 \cdot r $$After substituting $ d = 25 $ we have:
$$ 25 = 2 \cdot r $$ $$ r = \dfrac{ 25 }{ 2 } $$ $$ r = \frac{ 25 }{ 2 } $$STEP 2: find area $ A $
To find area $ A $ use formula:
$$ A = r^2 \cdot \pi $$After substituting $ r = \frac{ 25 }{ 2 } $ we have:
$$ A = \left(\frac{ 25 }{ 2 }\right)^2 \cdot \pi $$ $$ A = \frac{ 625 }{ 4 } \cdot \pi $$