Question

If the radius of a circle is increased by 20% then the area is inceeased by

Answer 1

Answer:

Let the original radius of circle be 10 cm

∴ Area of circle = πr²        ( let π be $\frac{22}{7}$)

                          = $\frac{22}{7}$ x 10 x 10

                          =  $\frac{2200}{7}$ cm²

New radius = 10 cm + 20% of 10 cm

                    = 12 cm

∴ Area of new circle = $\frac{22}{7}$ x 12 x 12

                                   = $\frac{3168}{7}$ cm²

∴ Difference in area = $\frac{3168}{7} - \frac{2200}{7}$ cm²

                                 = $\frac{968}{7}$ cm²

∴ Increase in area = $\frac{968}{7}$ x $\frac{7}{2200}$ x 100

                              = 44 %