At 9 a.m., Sean started from City Q and travelled towards City R and his speed remained constant throughout. At 10 a.m., Risa started her journey from City Q towards City R at an average speed of 90 km/h. Risa overtook Sean at 2 p.m. After overtaking, Risa carried on her journey at the same average speed and reached at City R at 3:50 p.m.
- Find Sean's average speed in km/h.
- What is the distance between the two cities?
(a)
From 10 a.m. to 2 p.m. = 4 h
Distance that Risa had travelled until Risa overtook Sean
= 4 x 90
= 360 km
From 9 a.m. to 2 p.m. = 5 h
Sean's average speed
= 360 ÷ 5
= 72 km/h
(b)
From 10 a.m. to 3:50 p.m. = 5 h 50 min
1 h = 60 min
5 h 50 min = 5
50 60
h = 5
56 h
Distance between the two cities
= 5
56 x 90
=
356 x 90
= 525 km
Answer(s): (a) 72 km/h; (b) 525 km