Find the radius of a circle whose circumference

Let the radius of a circle be r.

∴              Circumference of a circle = 2πr

Let the radii of two circles are r1 and r2 whose values are 15 cm and 18 cm respectively.

i.e.         r1 = 15cmand r2 = 18cm

Now, by given condition,

Circumference of circle = Circumference of first circle + Circumference of second circle

⇒                    2πr = 2πr1 + 2πr2

⇒                                 r = r1 + r2

⇒                                 r = 15 + 18

∴                           r = 33 cm

Hence, required radius of a circle is 33 cm.