At 7 a.m., David started from City C and travelled towards City D and his speed remained constant throughout. At 8 a.m., Gwen started her journey from City C towards City D at an average speed of 72 km/h. Gwen overtook David at 1 p.m. After overtaking, Gwen carried on her journey at the same average speed and reached at City D at 6:35 p.m.
- Find David's average speed in km/h.
- What is the distance between the two cities?
(a)
From 8 a.m. to 1 p.m. = 5 h
Distance that Gwen had travelled until Gwen overtook David
= 5 x 72
= 360 km
From 7 a.m. to 1 p.m. = 6 h
David's average speed
= 360 ÷ 6
= 60 km/h
(b)
From 8 a.m. to 6:35 p.m. = 10 h 35 min
1 h = 60 min
10 h 35 min = 10
35 60
h = 10
712 h
Distance between the two cities
= 10
712 x 72
=
12712 x 72
= 762 km
Answer(s): (a) 60 km/h; (b) 762 km