Tom and Andy started on a 45-km cycling trip at the same time. They cycled at the same speed for first 10 km. For the remaining 35 km, Tom cycled faster than Andy. He arrived at the finishing point 30 minutes before Andy who was 10 km behind him. Andy 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 Tom's average speed for the remaining 35 km of the trip in km/h?

(a)
60 min = 1 h
30 min =³⁰₆₀ h = ¹₂ 

Andy's average speed
= 10 ÷ ¹₂
= 20 km/h

Time that Andy took for the trip
= 45 ÷ 20
= 2⁵₂₀ h
= 2¹₄ h
= 2 h 15 min

2 h 15 min before 08 25 is 06 10.

(b)
To find the time that Tom took for the remaining 35 km of the trip, we need to use the time that Andy took subtract that of the time taken for first 10 km and the time that Tom was faster than Andy.

Time that Tom took for the remaining 35 km of the trip
= 2¹₄ - ¹₂ - ¹₂
= 1¹₄ h

Tom's average speed
= 35 ÷ 1¹₄
= 28 km/h

Answer(s): (a) 06 10; (b) 28 km/h