Question

if the ratio of the diameters of two circles is 2:5 find the ratio of their circumferences.

Answer 1

$$\begin{gathered} \mathrm{Let}{\mathrm{d}}_1\mathrm{and}{\mathrm{d}}_2\mathrm{be}\mathrm{the}\mathrm{diameters}\mathrm{of}\mathrm{the}\mathrm{given}\mathrm{circles}. \\ \mathrm{Now},\frac{{\mathrm{d}}_1}{{\mathrm{d}}_2}=\frac{2}{5} \\ \mathrm{Now}, \\ \frac{\mathrm{circumference}\mathrm{of}\mathrm{first}\mathrm{circle}}{\mathrm{circumference}\mathrm{of}\mathrm{second}\mathrm{circle}}=\frac{{\mathrm{\pi d}}_1}{{\mathrm{\pi d}}_2}=\frac{{\mathrm{d}}_1}{{\mathrm{d}}_2}=\frac{2}{5} \end{gathered}$$