Considering the least common factor of 15 and 18, it is found that they will depart from the central station at the same time at 11 AM.
To find the time that passes between the events happening at the same time, we need to find the least common multiple of the periods.
In this problem, the periods are of 15 and 18, hence their lcm is found as follows:
15 - 18|2
15 - 9|3
5 - 3|3
5 - 1|5
1 - 1
Hence:
lcm(15,18) = 2 x 3 x 3 x 5 = 90 minutes.
They will depart from the central station at the same time in 90 minutes from 9:30 AM, hence at 11 AM.
More can be learned about the least common factor at https://brainly.com/question/16314496
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