After traveling for 2 hours and 15 minutes, a train arrived in Kuala Lumpur from Singapore at 6.15 p.m. At what time did the train leave Singapore?

1. Subtract the travel time from the arrival time to find the departure time

Arrival time: $6.15$ p.m.
Travel time: $2$ hours $15$ minutes.
Subtracting $15$ minutes from $6.15$ p.m. gives $6.00$ p.m.
Subtracting $2$ hours from $6.00$ p.m. gives $4.00$ p.m.