At 7 a.m., Ian started from City S and travelled towards City T and his speed remained constant throughout. At 9 a.m., Erika started her journey from City S towards City T at an average speed of 72 km/h. Erika overtook Ian at 1 p.m. After overtaking, Erika carried on her journey at the same average speed and reached at City T at 5:20 p.m.

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

(a)
From 9 a.m. to 1 p.m. = 4 h

Distance that Erika had travelled until Erika overtook Ian
= 4 x 72
= 288 km

From 7 a.m. to 1 p.m. = 6 h

Ian's average speed
= 288 ÷ 6
= 48 km/h

(b)
From 9 a.m. to 5:20 p.m. = 8 h 20 min

1 h = 60 min
8 h 20 min = 8 ²⁰ ₆₀
 h = 8 ¹₃ h

Distance between the two cities
= 8 ¹₃ x 72
= ²⁵₃ x 72
= 600 km

Answer(s): (a) 48 km/h; (b) 600 km