question_answer

Find the area of the following circles:

(a) radius = 14 mm (Take\[\pi =\frac{22}{7}\])

(b) diameter = 49 m

(c) radius = 5 cm.

Answer:

We know that the area A of a circle of radius r is given by \[A=\pi {{r}^{2}}\] (a) Here,  r = 14 mm \[\therefore \] A = Area = \[\pi {{r}^{2}}\] \[=\left( \frac{22}{7}\times 14\times 14 \right)m{{m}^{2}}\] \[=\left( 22\times 2\times 14 \right)m{{m}^{2}}\] \[=\text{ }616\text{ }m{{m}^{2}}\]                                                                                                                  (b) Here, diameter = 49 m or, r = \[\frac{49}{2}m\] \[\therefore \] A = Area = \[\pi {{r}^{2}}\] \[=\left( \frac{22}{7}\times \frac{49}{2}\times \frac{49}{2} \right){{m}^{2}}\] \[=\left( \frac{11}{1}\times 7\times \frac{49}{2} \right){{m}^{2}}\] \[=\left( \frac{3773}{2} \right){{m}^{2}}=1886.5\,\,{{m}^{2}}\]                                                                      (c) Here,            r = 5 cm \[\therefore \] A = Area = \[\pi {{r}^{2}}\] \[=\left( \frac{22}{7}\times 5\times 5 \right)c{{m}^{2}}\] \[=\frac{550}{7}c{{m}^{2}}=78.57c{{m}^{2}}\]