Two cars 700 km apart at 9 am — one 1 h stop: Cars X and Y start from A and B, which are 700 km apart, at 9:00 am. Both run at 60 km/h. Car X stops from 10:00–11:00 am; car Y runs continuously. When do they meet?

Introduction / Context:We combine piecewise motion (one-hour halt) with relative speed to find the meeting time.

Given Data / Assumptions:

• Initial separation = 700 km
• Both speeds = 60 km/h
• X stops 10:00–11:00 am; Y continues uninterrupted.

Concept / Approach:Advance the timeline: first hour both move, next hour only Y moves, then both move again. Compute the remaining separation before the last phase and divide by relative speed.

Step-by-Step Solution:

Verification / Alternative check:Distances from A at meeting: X moved 1 h + 4 h 20 min = 5 h 20 min of motion ⇒ 320 km; Y moved 6 h 20 min ⇒ 380 km; sum = 700 km.

Why Other Options Are Wrong:They correspond to incorrect handling of the one-hour halt or miscomputed relative time.

Common Pitfalls:Subtracting 60 km twice or forgetting the continuous motion of Y during the stop.

Final Answer:3 : 20 pm