two tains of equal lengths take 10 seconds and 12 seconds respectively to cross a telegraph post . if the length of each train be 120 metres , in what time ( in seconds ) will they cross each other travelling in opposite direction ?
"sol . speed of the first train = [ 120 / 10 ] m / sec = 12 m / sec . speed of the second train = [ 120 / 12 ] m / sec = 10 m / sec . relative speed = ( 12 + 10 ) = m / sec = 22 m / sec . ∴ required time = ( 120 + 120 ) / 22 secc = 10.9 sec . answer c"
divide(add(120, 120), add(divide(120, 12), divide(120, 10)))