At 7 a.m., Luis started from City D and travelled towards City E and his speed remained constant throughout. At 10 a.m., Yen started her journey from City D towards City E at an average speed of 84 km/h. Yen overtook Luis at 1 p.m. After overtaking, Yen carried on her journey at the same average speed and reached at City E at 5:30 p.m.
- Find Luis'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 Yen had travelled until Yen overtook Luis
= 3 x 84
= 252 km
From 7 a.m. to 1 p.m. = 6 h
Luis's average speed
= 252 ÷ 6
= 42 km/h
(b)
From 10 a.m. to 5:30 p.m. = 7 h 30 min
1 h = 60 min
7 h 30 min = 7
30 60
h = 7
12 h
Distance between the two cities
= 7
12 x 84
=
152 x 84
= 630 km
Answer(s): (a) 42 km/h; (b) 630 km