Answer:
least waiting time = 18 mins
Explanation:
given as per question we know that 2nd bus start 10 min early than 1st bus
and both time frequency same = 30 min
1st bus time take = 1 hr 12 mins
and 2nd bus get waiting time 30 min - (10 + 12)
that is = 8 mins
so
we can say time arrival time for 1st bus = 8:32 and 9:02 and 9:32
by adding 30 mins
and
departure time for 2nd bus = 8:40 and 9:10 and 9:40
same like that 3rd bus leave every hour
and
service start on hour clock , a 10 mins early is = 7:10 am and 9 am
frequency of either half or 1 hour
so 2nd bus takes = 2 hour 40 mins
so waiting time is 60 - (10 - 40) = 10 min or 10 + 30 = 40 mins
so 1st bus waiting time is 8 mins so it take least time 10 mins for 2nd bus waiting time
as that
least waiting time = 8 + 10
least waiting time = 18 mins
