There are two trains, A and B which depart from a certain station.
The departure time of the first train and the last train both of A and B is same.
Train A departs from the station 21 times a day and Train B departs 31 times a day.
How many times do A and B depart at the same time ?
Answer
11 times
Solution
Number of departure intervals of A is 21 - 1 = 20 and that of B is 31 - 1 = 30.
If the time from first train to last train would be set to 60 minutes, interval time of A is 60/20 = 3 minutes and B is 60/30 = 2 minutes.
The interval time of departure at the same time is 6 minutes which is Least Common Multiple of 2 and 3.
Total number of same time departure is 60/6= 10 plus one which is first departure.
The departure time of the first train and the last train both of A and B is same.
Train A departs from the station 21 times a day and Train B departs 31 times a day.
How many times do A and B depart at the same time ?
Answer
11 times
Solution
Number of departure intervals of A is 21 - 1 = 20 and that of B is 31 - 1 = 30.
If the time from first train to last train would be set to 60 minutes, interval time of A is 60/20 = 3 minutes and B is 60/30 = 2 minutes.
The interval time of departure at the same time is 6 minutes which is Least Common Multiple of 2 and 3.
Total number of same time departure is 60/6= 10 plus one which is first departure.
