Question
Find the area $ A $ of a circle if diameter $d = 40\, \text{in}$.
Answer
$400\pi\, \text{in}^2$
Explanation
STEP 1: find radius $ r $
To find radius $ r $ use formula:
$$ d = 2 \cdot r $$After substituting $d = 40\, \text{in}$ we have:
$$ 40\, \text{in} = 2 \cdot r $$ $$ r = \dfrac{ 40\, \text{in} }{ 2 } $$ $$ r = 20\, \text{in} $$STEP 2: find area $ A $
To find area $ A $ use formula:
$$ A = r^2 \cdot \pi $$After substituting $r = 20\, \text{in}$ we have:
$$ A = \left( 20\, \text{in} \right)^{2} \cdot \pi $$ $$ A = 400\, \text{in}^2 \cdot \pi $$This page was created using
Circle Calculator