At 7 a.m., Lee started from City C and travelled towards City D and his speed remained constant throughout. At 9 a.m., Erika started her journey from City C towards City D at an average speed of 84 km/h. Erika overtook Lee at 1 p.m. After overtaking, Erika carried on her journey at the same average speed and reached at City D at 6:40 p.m.
- Find Lee's average speed in km/h.
- What is the distance between the two cities?
(a)
From 9 a.m. to 1 p.m. = 4 h
Distance that Erika had travelled until Erika overtook Lee
= 4 x 84
= 336 km
From 7 a.m. to 1 p.m. = 6 h
Lee's average speed
= 336 ÷ 6
= 56 km/h
(b)
From 9 a.m. to 6:40 p.m. = 9 h 40 min
1 h = 60 min
9 h 40 min = 9
40 60
h = 9
23 h
Distance between the two cities
= 9
23 x 84
=
293 x 84
= 812 km
Answer(s): (a) 56 km/h; (b) 812 km