At 8 a.m., Gabriel started from City C and travelled towards City D and his speed remained constant throughout. At 9 a.m., Gabby started her journey from City C towards City D at an average speed of 90 km/h. Gabby overtook Gabriel at 1 p.m. After overtaking, Gabby carried on her journey at the same average speed and reached at City D at 4:40 p.m.

1. Find Gabriel'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 Gabby had travelled until Gabby overtook Gabriel
= 4 x 90
= 360 km

From 8 a.m. to 1 p.m. = 5 h

Gabriel's average speed
= 360 ÷ 5
= 72 km/h

(b)
From 9 a.m. to 4:40 p.m. = 7 h 40 min

1 h = 60 min
7 h 40 min = 7 ⁴⁰ ₆₀
 h = 7 ²₃ h

Distance between the two cities
= 7 ²₃ x 90
= ²³₃ x 90
= 690 km

Answer(s): (a) 72 km/h; (b) 690 km