At 8 a.m., Riordan started from City R and travelled towards City S and his speed remained constant throughout. At 9 a.m., Diana started her journey from City R towards City S at an average speed of 78 km/h. Diana overtook Riordan at 2 p.m. After overtaking, Diana carried on her journey at the same average speed and reached at City S at 2:20 p.m.
- Find Riordan's average speed in km/h.
- What is the distance between the two cities?
(a)
From 9 a.m. to 2 p.m. = 5 h
Distance that Diana had travelled until Diana overtook Riordan
= 5 x 78
= 390 km
From 8 a.m. to 2 p.m. = 6 h
Riordan's average speed
= 390 ÷ 6
= 65 km/h
(b)
From 9 a.m. to 2:20 p.m. = 5 h 20 min
1 h = 60 min
5 h 20 min = 5
20 60
h = 5
13 h
Distance between the two cities
= 5
13 x 78
=
163 x 78
= 416 km
Answer(s): (a) 65 km/h; (b) 416 km