At 7 a.m., Justin started from City C and travelled towards City D and his speed remained constant throughout. At 10 a.m., Hilda started her journey from City C towards City D at an average speed of 68 km/h. Hilda overtook Justin at 1 p.m. After overtaking, Hilda carried on her journey at the same average speed and reached at City D at 4:15 p.m.

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

(a)
From 10 a.m. to 1 p.m. = 3 h

Distance that Hilda had travelled until Hilda overtook Justin
= 3 x 68
= 204 km

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

Justin's average speed
= 204 ÷ 6
= 34 km/h

(b)
From 10 a.m. to 4:15 p.m. = 6 h 15 min

1 h = 60 min
6 h 15 min = 6 ¹⁵ ₆₀
 h = 6 ¹₄ h

Distance between the two cities
= 6 ¹₄ x 68
= ²⁵₄ x 68
= 425 km

Answer(s): (a) 34 km/h; (b) 425 km