Answer:
60 minutes
Explanation:
Given the schedule above :
Red line arrives every 4 minutes
Blue line arrives every 5 minutes
Yellow line arrives every 6 minutes
All three just arrives at the train station ; when next will they all arrive at the train station at the same time.
Obtain the lowest common multiple of each arrov time :
Lowest common multiple of 4, 5, 6
_2___4___5___6
_2___2___5___3
_3___1___ 5 __ 3
_5___1___ 5 __ 1
_____1 ___1 ___1
Hence, lowest common multiple :(2 * 2 * 3 * 5) = 60
Hemce, they all arrive at the train station at the same time after 60 minutes