question_answer 1)

A gardener wants to fence a circular garden of diameter 21 m. Find the length of the rope he needs to purchase, if he makes 2 rounds offence. Also find the cost of the rope, if it cost ` 4 per meter. \[\left( \text{Take  }\!\!\pi\!\!\text{  = }\frac{\text{22}}{\text{7}} \right)\]

Answer:

                Radius of the circular garden (r) = 21 m \[\Rightarrow \]               Radius of the circular garden (r) \[=\frac{21}{2}\text{m}\] \[\therefore \]                  Circumference of the circular garden                 \[=2\pi r\]                 \[\text{= 2  }\!\!\times\!\!\text{  }\frac{\text{22}}{\text{7}}\text{  }\!\!\times\!\!\text{  }\frac{\text{21}}{\text{2}}\text{m = 66 m}\] \[\Rightarrow \]               Length of the rope to make 1 round of fence \[=\text{66 m}\] \[\Rightarrow \]               Length of the rope to make 2 rounds of fence \[=\text{66}\times \text{2m}=\text{132 m}\] \[\therefore \]                  Cost of the rope = ` \[132\times 4\]                               =  ` 528