At 8 a.m., Bobby started from City Z and travelled towards City A and his speed remained constant throughout. At 9 a.m., Sabrina started her journey from City Z towards City A at an average speed of 72 km/h. Sabrina overtook Bobby at 2 p.m. After overtaking, Sabrina carried on her journey at the same average speed and reached at City A at 3:30 p.m.

1. Find Bobby'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 Sabrina had travelled until Sabrina overtook Bobby
= 5 x 72
= 360 km

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

Bobby's average speed
= 360 ÷ 6
= 60 km/h

(b)
From 9 a.m. to 3:30 p.m. = 6 h 30 min

1 h = 60 min
6 h 30 min = 6 ³⁰ ₆₀
 h = 6 ¹₂ h

Distance between the two cities
= 6 ¹₂ x 72
= ¹³₂ x 72
= 468 km

Answer(s): (a) 60 km/h; (b) 468 km