Question

The inner circumference of a circular track is $264m$ and the width of the track is $7m$. Find :
the cost of fencing the outer circumference at the rate of $Rs50perm$.

Answer 1

Let $r$ be the radius of the inner track.

Inner circumference of track $=2\pi r=264m\left(\text{Given}\right)$

$\Rightarrow 2\times \frac{22}{7}\times r=264$

$\Rightarrow r=264\times \frac{7}{2\times 22}$

$\Rightarrow r=42m$

Width of track $\left(w\right)=7m\left(\text{Given}\right)$

$\therefore$ Outer radius $\left(R\right)=r+w$

$=42+7=49m$

Therefore,

Outer circumeference of track $=2\pi R$

$=2\times \frac{22}{7}\times 49=308m$

Cost of fencing $=Rs.50$ per meter

Therefore,

Cost of fencing the outer circumference of track $=50\times 308=Rs.15400$