When three identical bulbs of 60 W, 200 V rating are connected in series to a 200 V supply, the power drawn by them will be

Let R1, R2 and R3 be the resistances of three bulbs, respectively.In series order,R = R1 + R2 + R3But R = V2/P and supply voltage is the same as the rated voltage∴    V2P = V2P1 +  V2P2 + V2P3or   1P =160 +160 +160 or  P=603 =20  W