At 8 a.m., Lee started from City M and travelled towards City N and his speed remained constant throughout. At 9 a.m., Gillian started her journey from City M towards City N at an average speed of 72 km/h. Gillian overtook Lee at 2 p.m. After overtaking, Gillian carried on her journey at the same average speed and reached at City N at 3:30 p.m.

1. Find Lee's average speed in km/h.
2. What is the distance between the two cities?

(a)
From 9 a.m. to 2 p.m. = 5 h

Distance that Gillian had travelled until Gillian overtook Lee
= 5 x 72
= 360 km

From 8 a.m. to 2 p.m. = 6 h

Lee's average speed
= 360 ÷ 6
= 60 km/h

(b)
From 9 a.m. to 3:30 p.m. = 6 h 30 min

1 h = 60 min
6 h 30 min = 6 ³⁰ ₆₀
 h = 6 ¹₂ h

Distance between the two cities
= 6 ¹₂ x 72
= ¹³₂ x 72
= 468 km

Answer(s): (a) 60 km/h; (b) 468 km