Lee and Mark started on a 35-km cycling trip at the same time. They cycled at the same speed for first 5 km. For the remaining 30 km, Lee cycled faster than Mark. He arrived at the finishing point 20 minutes before Mark who was 5 km behind him. Mark did not change his speed throughout and completed it at 08 30.
- At what time did the trip begin? Give the answer in 12-hour format.
- What was Lee's average speed for the remaining 30 km of the trip in km/h?
(a)
60 min = 1 h
20 min =
2060 h =
13 Mark's average speed
= 5 ÷
13 = 15 km/h
Time that Mark took for the trip
= 35 ÷ 15
= 2
515 h
= 2
13 h
= 2 h 20 min
2 h 20 min before 08 30 is 06 10.
(b)
To find the time that Lee took for the remaining 30 km of the trip, we need to use the time that Mark took subtract that of the time taken for first 5 km and the time that Lee was faster than Mark.
Time that Lee took for the remaining 30 km of the trip
= 2
13 -
13 -
13 = 1
23 h
Lee's average speed
= 30 ÷ 1
23 = 18 km/h
Answer(s): (a) 06 10; (b) 18 km/h