CM.The thickness of the ring is 3.5 cm.Circumference of circle is 2 × pi × rThe inner circumference of a CIRCULAR ring is 22 cm.So, 2 × pi × R = 22 cm.⇒ r = \({22 \over 2 pi}\) = 3.5 cm.The OUTER circumference of a circular ring is 44 cm.So, 2 × pi × r = 44 cm.⇒ r = \({44 \over 2pi}\) = 7 cm.So, The thickness of the ring = 7 - 3.5 = 3.5 cm.