Question

Find the circumference and area of a circle with radius 4 cm. Express your answer in terms of π.

A: 8π cm; 16π cm2
B: 8π cm; 24π cm2
C: 16π cm; 50π cm2
D: 16π cm; 24π cm2

Answer 1

A. 8π cm; 16π cm2

Explanation:

circumference: C = 2πr = 2(4)π = 8π cm

area: A = π(r^2) = (4^2)π = 16π cm^2

Answer 2

The correct answer is option (A) 8π cm; 16π cm².

Solution :

Finding the circumference of circle by substituting the values in the formula :

`\longrightarrow{\pmb{\sf{C_((Circle)) = 2\pi r}}}`

• 
  `\pink\star` C = Circumference
• 
  `\pink\star` π = 3.14 or 22/7
• 
  `\pink\star` r = radius

`\longrightarrow{\sf{C_((Circle)) = 2 * \pi * 4}}`

`\longrightarrow{\sf{C_((Circle)) = 8 * \pi }}`

`\longrightarrow{\sf{C_((Circle)) = 8\pi }}`

`\star{\underline{\boxed{\sf{\red{C_((Circle)) = 8\pi \: cm}}}}}`

Hence, the circumference of circle is 8π cm.

`\begin{gathered}\end{gathered}`

Finding the area of circle by substituting the values in the formula :

`\longrightarrow{\pmb{\sf{A_((Circle)) = \pi{r}^(2)}}}`

• 
  `\purple\star` A = Area
• 
  `\purple\star` π = 3.14 or 22/7
• 
  `\purple\star` r = radius

`\longrightarrow{\sf{A_((Circle)) = \pi{r}^(2)}}`

`\longrightarrow{\sf{A_((Circle)) = \pi{(4)}^(2)}}`

`\longrightarrow{\sf{A_((Circle)) = \pi{(4 * 4)}}}`

`\longrightarrow{\sf{A_((Circle)) = \pi{(16)}}}`

`\longrightarrow{\sf{A_((Circle)) = \pi * 16}}`

`\longrightarrow{\sf{A_((Circle)) = 16\pi}}`

`\star{\underline{\boxed{\sf{\red{A_((Circle)) = 16\pi \: {cm}^(2)}}}}}`

Hence, the area of circle is 16π cm².

`\rule{300}{2.5}`