Three concentric circles have radii (in cm) `a, b` and `c`, where `a < b < c`. If `a = 8` and `b = 9` and the middle circle bisects the area between the other two circles, then the value of `c `is

Three concentric circles have radii x cm, 10 cm and 5 cm such that x > 10 > 5. If the area enclosed by circles with radii x cm and 10 cm is the same as the area enclosed by the circles with radii 10 cm and 5 cm, find the area of the largest circle.

Two concentric circles have radii 20 cm and 15 cm. Find the area of ring shaped region

Three concentric spherical shells have radii a, b and c(a lt b lt c) and have surface charge densities sigma, -sigam and sigma respectively. If V_(A), V_(B) and V_(C) denote the potentials of the three shells, then for c = a + b , we have

Three concentric spherical shells have radii a, b and c(a lt b lt c) and have surface charge densities sigma, -sigma and sigma respectively. If V_(A), V_(B) and V_(C) denote the potentials of the three shells, then for c = q + b , we have

Three concentric spherical shells have radii a, b and c(a lt b lt c) and have surface charge densities sigma, - sigma and sigma respectively. If V_(A), V_(B) and V_(C) denote the potentials of the three shells, then for c = a + b , we have

Two concentric circles are of radii 7cm and r cm respectively, where r gt 7 . A chord of the larger circle of length 46cm , touches the smaller circle. Find the value of r .