Train A arrives at central station on the hour and every 12 minutes. Train B arrives o the hour and every 15 minutes. When do both trains arrive at the same time?

Every 30 hours

Step-by-step explanation:

Train A arrives at central station on the hour and every 12 minutes, you mean with that on every 72 minutes

Train B arrives at central station on the hour and every 15 minutes, you mean with that on every 75 minutes

In accordance with the given, the smallest number containing numbers 72 and 75 is 1800 minutes.

When we convert this number of minutes in hours we get:

1800 / 60 = 30 hours

God with you!