Question

The diameter of a circle is 42 cm, find its perimeter. If the perimeter of the circle is
22
doubled, what will be the radius of the new circle.​

Answer 1

Answer:

Here's the solution

Hope it helps

Answer 2

Given :

• Diameter of Circle = 42cm.
• Perimeter of Circle 22cm.

To Find :

• Radius of new circle if perimeter is doubled.

Solution :

$\longmapsto\tt{Diameter=42cm}$

$\longmapsto\tt{Radius=\cancel\dfrac{42}{2}=21cm}$

Using Formula :

$\longmapsto\tt\boxed{Perimeter\:of\:Circle=2\pi{r}}$

Putting Values :

$\longmapsto\tt{2\times\dfrac{22}{\cancel{7}}\times{\cancel{21}}}$

$\longmapsto\tt{2\times{22}\times{3}}$

$\longmapsto\tt\bold{132{cm}^{2}}$

If Perimeter is doubled :

$\longmapsto\tt{132\times{2}}$

$\longmapsto\tt\bold{264{cm}^{2}}$

A.T.Q :

$\longmapsto\tt{264=2\pi{r}}$

$\longmapsto\tt{264=2\times\dfrac{22}{7}\times{r}}$

$\longmapsto\tt{264\times{7}=44r}$

$\longmapsto\tt{1848=44r}$

$\longmapsto\tt{r=\cancel\dfrac{1848}{44}}$

$\longmapsto\tt\bold{r=42cm}$

So , The radius of the new circle will be 42cm..