Sir, The diameter of a metal ring is D and the coefficient of linear expansion is y. The temperature of the ring is increased by 1 degree Celsius. What is the increase in area of the ring? I solved it the following way: Coefficient of superficial expansion = 2y Initial area of the ring(A) = [(pi)D^2]/4 Increase in diameter of the ring = Dy Increase in area of the ring = A x (2y) = [(pi)D^2]/4 x 2y = [(pi)(D^2)y]/2 But the answer given in my book is 2(D^2)y. Please help. Here the symbol ^ stands for power.