Oliver and Owen started on a 48-km cycling trip at the same time. They cycled at the same speed for first 5 km. For the remaining 43 km, Oliver cycled faster than Owen. He arrived at the finishing point 20 minutes before Owen who was 5 km behind him. Owen did not change his speed throughout and completed it at 08 25.

1. At what time did the trip begin? Give the answer in 12-hour format.
2. What was Oliver's average speed for the remaining 43 km of the trip in km/h?

(a)
60 min = 1 h
20 min =²⁰₆₀ h = ¹₃ 

Owen's average speed
= 5 ÷ ¹₃
= 15 km/h

Time that Owen took for the trip
= 48 ÷ 15
= 3³₁₅ h
= 3¹₅ h
= 3 h 12 min

3 h 12 min before 08 25 is 05 13.

(b)
To find the time that Oliver took for the remaining 43 km of the trip, we need to use the time that Owen took subtract that of the time taken for first 5 km and the time that Oliver was faster than Owen.

Time that Oliver took for the remaining 43 km of the trip
= 3¹₅ - ¹₃ - ¹₃
= 2⁸₁₅ h

Oliver's average speed
= 43 ÷ 2⁸₁₅
= 16³⁷₃₈ km/h

Answer(s): (a) 05 13; (b) 16³⁷₃₈ km/h