Question

if the redius of a circle is increased by 50%, its perimeter is increased by..?

Answer 1

Let old radius be r cm

So, old Perimeter = 2πr

Now, new radius = r + r/2 = 3r/2

so, New Perimeter = 2π*3r/2
                              = 3πr

so, change in perimeter = 3πr - 2πr
                                       = πr(3-2)
                                       = πr

so, Percentage increased = πr*100/2πr = 100πr/2πr = 50 %