Question

For traffic control, a CCTV camera is fixed on a straight and vertical pole. The camera can see $113m$ distance straight line from the top. If the area visible by the camera around the pole is $39424m^2$, then find the height of the pole.

Answer 1

Area surrounded $=39429{cm}^2$

$\pi r^2=39429\frac{22}{7}{r}^2=39429\Rightarrow r^2=12544\Rightarrow r=\sqrt{12544}=112$

Let the height of pole be $AO$

using pythagoras theorem

${\left(AO\right)}^2+r^2={\left(AB\right)}^2{\left(AO\right)}^2+12544={\left(113\right)}^2{\left(AO\right)}^2=225\Rightarrow AO=15m$