At 8 a.m., Riordan started from City R and travelled towards City S and his speed remained constant throughout. At 9 a.m., Olivia started her journey from City R towards City S at an average speed of 66 km/h. Olivia overtook Riordan at 2 p.m. After overtaking, Olivia carried on her journey at the same average speed and reached at City S at 6:30 p.m.

1. Find Riordan'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 Olivia had travelled until Olivia overtook Riordan
= 5 x 66
= 330 km

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

Riordan's average speed
= 330 ÷ 6
= 55 km/h

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

1 h = 60 min
9 h 30 min = 9 ³⁰ ₆₀
 h = 9 ¹₂ h

Distance between the two cities
= 9 ¹₂ x 66
= ¹⁹₂ x 66
= 627 km

Answer(s): (a) 55 km/h; (b) 627 km