Question

If the area of a circle is 154 cm², then its perimeter is __________.

Answer 1

Let the radius of the circle be r cm.

Area of the circle = 154 cm²

$$\begin{gathered} \Rightarrow \mathrm{\pi }{r}^2=154{\mathrm{cm}}^2 \\ \Rightarrow \frac{22}{7}\times r^2=154 \\ \Rightarrow r=\sqrt{\frac{154\times 7}{22}}=7\mathrm{cm} \end{gathered}$$

∴ Perimeter of the circle

= Circumference of the circle

$$\begin{gathered} =2\mathrm{\pi }r \\ =2\times \frac{22}{7}\times 7 \\ =44\mathrm{cm} \end{gathered}$$

If the area of a circle is 154 cm², then its perimeter is ___44 cm___.