Complete question :
Mulder and Scully are driving to the same town. Mulder leaves the office at 9:30 a.m. averaging 51 mph. Scully leaves at 10:00 a.m., following the same path and averaging 57 mph. At what time will Scully catch up with Mulder?
Answer:
2:15 p.m
Explanation:
Given the following :
Mulder :
Speed = 51mph
Time he left office = 9:30 a.m
Scully :
Speed = 57mph
Time she left office = 10:00 a.m
Time difference = (10:00 - 9:30)a.m = 30 minutes = half an hour = 0.5 hour
Let Scully's travel time when she catches up = s
Therefore, Mulder's time at the same moment = (s + 0.5)
Recall:
distance = speed × time
Hence,
Scully's distance : 57 * s = 57s
Mulder's distance : 51 * (s + 0.5)
Equating both :
57s = 51(s + 0.5)
57s = 51s + 25.5
57s - 51s = 25.5
6s = 25.5
s = 25.5 / 6
s = 4.25 hours
Hence scully will catch up with Mulder after 4.25 hours
10:00am + 4.25 hours = 2:15p.m