At 9 a.m., Carl started from City R and travelled towards City S and his speed remained constant throughout. At 10 a.m., Mary started her journey from City R towards City S at an average speed of 72 km/h. Mary overtook Carl at 3 p.m. After overtaking, Mary carried on her journey at the same average speed and reached at City S at 1:50 p.m.

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

(a)
From 10 a.m. to 3 p.m. = 5 h

Distance that Mary had travelled until Mary overtook Carl
= 5 x 72
= 360 km

From 9 a.m. to 3 p.m. = 6 h

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

(b)
From 10 a.m. to 1:50 p.m. = 3 h 50 min

1 h = 60 min
3 h 50 min = 3 ⁵⁰ ₆₀
 h = 3 ⁵₆ h

Distance between the two cities
= 3 ⁵₆ x 72
= ²³₆ x 72
= 276 km

Answer(s): (a) 60 km/h; (b) 276 km