the diameters of two circles are 38cm and 18cm.the diameter of the circle whose circumference is equal to sum of the circumference of the two circles is?
D = 38 R = 19
d = 18 r =9
2piR + 2pir = 2piR'
2pi ( R +r) = 2 pi R'
2 pi gets cancelled
R+r =R'
19 +9 =R'
so R' = 28