At 9 a.m., Perry started from City B and travelled towards City C and his speed remained constant throughout. At 10 a.m., Risa started her journey from City B towards City C at an average speed of 84 km/h. Risa overtook Perry at 3 p.m. After overtaking, Risa carried on her journey at the same average speed and reached at City C at 4:50 p.m.

1. Find Perry'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 Risa had travelled until Risa overtook Perry
= 5 x 84
= 420 km

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

Perry's average speed
= 420 ÷ 6
= 70 km/h

(b)
From 10 a.m. to 4:50 p.m. = 6 h 50 min

1 h = 60 min
6 h 50 min = 6 ⁵⁰ ₆₀
 h = 6 ⁵₆ h

Distance between the two cities
= 6 ⁵₆ x 84
= ⁴¹₆ x 84
= 574 km

Answer(s): (a) 70 km/h; (b) 574 km