a train 850 m long is running at a speed of 78 km / hr . if it crosses a tunnel in 1 min , then the length of the tunnel is ?
"speed = 78 * 5 / 18 = 65 / 3 m / sec . time = 1 min = 60 sec . let the length of the train be x meters . then , ( 850 + x ) / 60 = 65 / 3 x = 450 m . answer : option b"
divide(850, multiply(subtract(78, 1), const_0_2778))