It is 9 p.m., when can Himanshu get next bus for A from B ?
I. Buses for A leave after every 30 minutes, till 10 p.m.
II. Fifteen minutes ago, one bus has left for A.
If the data in both statements I and II together are necessary to answer the question
II reveals that the previous bus had left at 8.45 p.m. As given in I, the next bus would leave after 30 minutes i.e. at 9.15 p.m.