question_answer 28)

The circumference of a circle is 31.4 cm. Find the radius and the area of the circle? \[\left( \text{Take }\pi =\text{3}.\text{14} \right)\]

Answer:

                Let the radius of the circle be r cm. Circumference of the circle  \[=\text{31}.\text{4 cm}\]   Given \[\Rightarrow \]         \[2\pi r=31.4\] \[\Rightarrow \]         \[2\times 3.14\times r=31.4\] \[\Rightarrow \]               \[r=\frac{31.4}{2\times 3.14}=\text{5cm}\] Area of the circle \[=\pi {{r}^{2}}\] \[\text{= 3}\text{.14 }\!\!\times\!\!\text{  }{{\text{5}}^{\text{2}}}\text{c}{{\text{m}}^{\text{2}}}\] \[\text{= 3}\text{.14  }\!\!\times\!\!\text{  25 c}{{\text{m}}^{\text{2}}}\] \[\text{=78}\text{.5 c}{{\text{m}}^{2}}\]