two trains of length 100 m and 200 m are 100 m apart . they start moving towards each other on parallel tracks , at speeds 90 kmph and 108 kmph . in how much time will the trains cross each other ?
"relative speed = ( 90 + 108 ) * 5 / 18 = 11 * 5 = 55 mps . the time required = d / s = ( 100 + 100 + 200 ) / 55 = 400 / 55 = 80 / 11 sec . answer : e"
divide(100, multiply(add(90, 108), const_0_2778))