At 9 a.m., Seth started from City M and travelled towards City N and his speed remained constant throughout. At 10 a.m., Gem started her journey from City M towards City N at an average speed of 80 km/h. Gem overtook Seth at 2 p.m. After overtaking, Gem carried on her journey at the same average speed and reached at City N at 6:30 p.m.

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

(a)
From 10 a.m. to 2 p.m. = 4 h

Distance that Gem had travelled until Gem overtook Seth
= 4 x 80
= 320 km

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

Seth's average speed
= 320 ÷ 5
= 64 km/h

(b)
From 10 a.m. to 6:30 p.m. = 8 h 30 min

1 h = 60 min
8 h 30 min = 8 ³⁰ ₆₀
 h = 8 ¹₂ h

Distance between the two cities
= 8 ¹₂ x 80
= ¹⁷₂ x 80
= 680 km

Answer(s): (a) 64 km/h; (b) 680 km