Bobby and Cole started on a 60-km cycling trip at the same time. They cycled at the same speed for first 12 km. For the remaining 48 km, Bobby cycled faster than Cole. He arrived at the finishing point 40 minutes before Cole who was 12 km behind him. Cole did not change his speed throughout and completed it at 08 30.

1. At what time did the trip begin? Give the answer in 12-hour format.
2. What was Bobby's average speed for the remaining 48 km of the trip in km/h?

(a)
60 min = 1 h
40 min =⁴⁰₆₀ h = ²₃ 

Cole's average speed
= 12 ÷ ²₃
= 18 km/h

Time that Cole took for the trip
= 60 ÷ 18
= 3⁶₁₈ h
= 3¹₃ h
= 3 h 20 min

3 h 20 min before 08 30 is 05 10.

(b)
To find the time that Bobby took for the remaining 48 km of the trip, we need to use the time that Cole took subtract that of the time taken for first 12 km and the time that Bobby was faster than Cole.

Time that Bobby took for the remaining 48 km of the trip
= 3¹₃ - ²₃ - ²₃
= 2 h

Bobby's average speed
= 48 ÷ 2
= 24 km/h

Answer(s): (a) 05 10; (b) 24 km/h