Question

Two trains along th esame straight rails moving with constant speed 60 km/hr resp. towards each other . If at time t=0 the distance between them is 90 km the time when they collide is

Answer 1

$$\begin{gathered} Velocityofapproachoftwotrainsv=60+60=120km/hr \\ distnacebetweenthemd=90km \\ timetakentocollide \\ t=\frac{d}{v}=\frac{90}{120} \\ t=3/4hr \\ t=45min \end{gathered}$$