An athlete completes one round of circular track of diameter 200 m in 40s. What will be the distance covered at the end of 2 minute 40 seconds? 

The diameter of the circular track$=200\mathit{ m}$
Radius of circular track,  $\mathit{r }= 100\mathit{ m}$

$\mathrm{Distance} \mathrm{travelled} \mathrm{by} \mathrm{athlete} \mathrm{in} 40 \mathrm{s} = \mathrm{circumference} \mathrm{of} \mathrm{the} \mathrm{circle}$
$=\mathrm{ }2\pi r$
$= 2\pi \mathit{ }\times 100\mathit{ m}$

$= 200\pi \mathit{ m}$
Distance traveled in $1\mathit{ s}$$=\frac{200\pi }{40}$

 $= 5\pi m$
Distance covered in $2$ minutes and $40\mathit{ s}$ i.e. in $160\mathit{ s},$
 $=5\pi \mathit{ }\times 160$
$=\mathrm{ }2513 \mathrm{m}$
Thus, the distance traveled by the athlete at the end is $2513 \mathrm{m}.$