At 9 a.m., Jack started from City Y and travelled towards City Z and his speed remained constant throughout. At 10 a.m., Min started her journey from City Y towards City Z at an average speed of 72 km/h. Min overtook Jack at 1 p.m. After overtaking, Min carried on her journey at the same average speed and reached at City Z at 1:45 p.m.
- Find Jack's average speed in km/h.
- What is the distance between the two cities?
(a)
From 10 a.m. to 1 p.m. = 3 h
Distance that Min had travelled until Min overtook Jack
= 3 x 72
= 216 km
From 9 a.m. to 1 p.m. = 4 h
Jack's average speed
= 216 ÷ 4
= 54 km/h
(b)
From 10 a.m. to 1:45 p.m. = 3 h 45 min
1 h = 60 min
3 h 45 min = 3
45 60
h = 3
34 h
Distance between the two cities
= 3
34 x 72
=
154 x 72
= 270 km
Answer(s): (a) 54 km/h; (b) 270 km