Two trains crossed each other in 10 sec when the are running in opposite directions. The length of one of the trains is 510 m, while the ratio of their speed is 3 ∶ 2. Approximately in how many seconds the faster train will cross a platform which is half of its length if it's given the speed of the slower train is 129.6 km/hr and the longer train travels at a slower speed?
1
15.54 sec
2
21.25 sec
3
10.83 sec
4
18.41 sec
5
22.56 sec