There are two concentric circles as shown in the following figure. The circumference of outer circle is $132 \mathrm{cm}$ and circumference of the inner circle is $88 \mathrm{cm}$. Find the differences between their radii i.e., $\left(\mathrm{R}-\mathrm{r}\right)$

 

A piece of wire in the form of a rectangle of $8.9 \mathrm{cm}$ long and $54 \mathrm{mm}$ broad is reshaped and bent in the form of a circle. Find the radius of the circle in $\mathrm{mm}$.

A piece of wire is bent in the shape of a square of side $11 \mathrm{cm}$. It is rebent to form a circular ring. What is the diameter of the ring?

[Hint: Circumference of the circle $=$ Perimeter of the square]

A piece of wire is in the form of a rectangle whose length and breadth are $40 \mathrm{cm}$ and $26 \mathrm{cm}$ respectively. It is rebent in the form of a circle. Find the radius of the circle.

In the adjoining figure, the area of the cross roads is