Question

The radii of two circles are 5 cm and 12 cm respectively . What is the diameter of the circle which has circumference equal to the difference of the circumference equal to the difference of the circumferences of the two circles

Answer 1

2πr=2π($r_{1}-r_{2}$)
r=$r_{1}-r_{2}$
r=12-5
r=7cm

∴Diameter=2r=14cm