A bus for Delhi leaves every thirty minutes from a bus stand. An enquiry clerk told a passenger that the bus had already left ten…

Question

A bus for Delhi leaves every thirty minutes from a bus stand. An enquiry clerk told a passenger that the bus had already left ten minutes ago and the next bus will leave at 9:35 am. At what time did the enquiry clerk give this information to the passenger?

1. A. 9:15 am (Correct answer)
2. B. 9:08 am
3. C. 8:55 am
4. D. 9:10 am

Correct Answer

Option A — 9:15 am

Detailed Solution & Explanation

The correct answer is 9:15 am.

Key Points

• Buses leave every 30 minutes, and the next departure is at 9:35 am.
• The previous bus therefore left at 9:35 − 30 minutes = 9:05 am.
• The clerk says that bus left ten minutes ago, so the time of speaking is 9:05 + 10 = 9:15 am.

Additional Information

• Work backwards from the fixed reference — here the known next departure — rather than forwards from the unknown present.
• Verify the answer against both facts: at 9:15, the 9:05 bus left 10 minutes earlier and the 9:35 bus is 20 minutes away. Both hold.
• The same method covers questions on train timetables, shift rotations and recurring appointments.