A postal runner on foot leaves Post Office A at 6:00 a.m. toward Post Office B at a steady speed of 6 km/h. A scooter departs from Post Office B toward A at 7:30 a.m. at a speed of 42 km/h. The distance between A and B is 210 km. At what clock time will they meet? (Round minutes and seconds to the nearest second)
Show answer & explanation
Correct answer: B
Explanation
Given:
Postman's speed = 6 km/h
Scooter's speed = 42 km/h
Total distance = 210 km
Postman's start time = 6:00 a.m.
Scooter's start time = 7:30 a.m.
According to the formula:
Relative speed = 6 + 42 = 48 km/h
Distance = Speed × Time
Time elapsed from 6:00 to 7:30 = 1.5 hours
Distance covered by the postman during this time = 6 × 1.5 = 9 km
Remaining distance = 210 − 9 = 201 km
Meeting time (after 7:30) = 201 / 48 = 4.1875 hours
0.1875 hours = 0.1875 × 60 = 11.25 minutes
0.25 minutes = 0.25 × 60 = 15 seconds
Therefore, time = 4 hours 11 minutes 15 seconds
Total time = 7:30 + 4:11:15 = 11:41:15 a.m.