aap bus service centre has two field services that start together at 8 a.m. bus leaves at 15 minutes interval while bus believes at 20 minutes interval on a particular day how many times do both services live together from 8 a.m. to 11 a.m.
15 and 20 are both factors of 60
so the buses leave together on every whole hour ... 8, 9, 10, 11