Question

Please answer me....
(I'll mark the answer as Brainliest)​

Answer 1

Answer:

=> r + 2πr = 51

=> r = 51/(1+6.28)

=> r = 51/7.28

=> r = 7cm

=> A = πr²

=> A = 22/7 * 49

=> A = 22*7

=> A = 154 cm²

Answer 2

Let the radius of the circle be $\displaystyle\sf {r\ (in\ cm),}$ then it's circumference will be $\displaystyle\sf {2\pi r}$ and the area will be $\displaystyle\sf {\pi r^2.}$

Given that the sum of the radius and the circumference is 51 cm.

$\displaystyle\longrightarrow\sf{r+2\pi r=51}$

$\displaystyle\longrightarrow\sf{r(1+2\pi)=51}$

$\displaystyle\longrightarrow\sf{r=\dfrac {51}{1+2\pi}}$

Taking $\displaystyle\sf {\pi=\dfrac {22}{7},}$

$\displaystyle\longrightarrow\sf{r=\dfrac {51}{1+2\times\dfrac {22}{7}}}$

$\displaystyle\longrightarrow\sf{r=\dfrac {51}{\left (\dfrac {51}{7}\right)}}$

$\displaystyle\longrightarrow\sf{r=7\ cm}$

Then, area is,

$\displaystyle\longrightarrow\sf{A=\pi r^2}$

$\displaystyle\longrightarrow\sf{A=\dfrac {22}{7}\times 7^2}$

$\displaystyle\longrightarrow\sf {\underline {\underline {A=154\ cm^2}}}$

Hence area is 154 cm².