Question

if an angle is the complement of 4/5 of right angle, then find its measure?

Answer 1

$$\begin{gathered} \mathrm{Let}\mathrm{the}\mathrm{required}\mathrm{angle}=\mathrm{x} \\ \mathrm{Now},\mathrm{four}\mathrm{fifth}\mathrm{of}\mathrm{the}\mathrm{right}\mathrm{angle}=\frac{4}{5}\mathrm{of}90°=\frac{4}{5}\times 90°=72° \\ \mathrm{Now},\mathrm{complement}\mathrm{of}\mathrm{required}\mathrm{angle}=90°-\mathrm{x} \\ \mathrm{Now},\mathrm{according}\mathrm{to}\mathrm{question}: \\ 90°-\mathrm{x}=72° \\ \Rightarrow \mathrm{x}=90°-72°=18° \\ \mathrm{So},\mathrm{required}\mathrm{angle}=18° \end{gathered}$$