At 9 a.m., Justin started from City J and travelled towards City K and his speed remained constant throughout. At 10 a.m., Betty started her journey from City J towards City K at an average speed of 84 km/h. Betty overtook Justin at 1 p.m. After overtaking, Betty carried on her journey at the same average speed and reached at City K at 6:15 p.m.
- Find Justin'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 Betty had travelled until Betty overtook Justin
= 3 x 84
= 252 km
From 9 a.m. to 1 p.m. = 4 h
Justin's average speed
= 252 ÷ 4
= 63 km/h
(b)
From 10 a.m. to 6:15 p.m. = 8 h 15 min
1 h = 60 min
8 h 15 min = 8
15 60
h = 8
14 h
Distance between the two cities
= 8
14 x 84
=
334 x 84
= 693 km
Answer(s): (a) 63 km/h; (b) 693 km