Question
Find the area $ A $ of a circle if diameter $d = 15\, \text{cm}$.
Answer
$\dfrac{ 225 }{ 4 }\pi\, \text{cm}^2$
Explanation
STEP 1: find radius $ r $
To find radius $ r $ use formula:
$$ d = 2 \cdot r $$After substituting $d = 15\, \text{cm}$ we have:
$$ 15\, \text{cm} = 2 \cdot r $$ $$ r = \dfrac{ 15\, \text{cm} }{ 2 } $$ $$ r = \frac{ 15 }{ 2 }\, \text{cm} $$STEP 2: find area $ A $
To find area $ A $ use formula:
$$ A = r^2 \cdot \pi $$After substituting $r = \dfrac{ 15 }{ 2 }\, \text{cm}$ we have:
$$ A = \left( \frac{ 15 }{ 2 }\, \text{cm} \right)^{2} \cdot \pi $$ $$ A = \frac{ 225 }{ 4 }\, \text{cm}^2 \cdot \pi $$This page was created using
Circle Calculator