John and Ahmad started on a 50-km cycling trip at the same time. They cycled at the same speed for first 10 km. For the remaining 40 km, John cycled faster than Ahmad. He arrived at the finishing point 40 minutes before Ahmad who was 10 km behind him. Ahmad did not change his speed throughout and completed it at 09 30.
- At what time did the trip begin? Give the answer in 12-hour format.
- What was John's average speed for the remaining 40 km of the trip in km/h?
(a)
60 min = 1 h
40 min =
4060 h =
23 Ahmad's average speed
= 10 ÷
23 = 15 km/h
Time that Ahmad took for the trip
= 50 ÷ 15
= 3
515 h
= 3
13 h
= 3 h 20 min
3 h 20 min before 09 30 is 06 10.
(b)
To find the time that John took for the remaining 40 km of the trip, we need to use the time that Ahmad took subtract that of the time taken for first 10 km and the time that John was faster than Ahmad.
Time that John took for the remaining 40 km of the trip
= 3
13 -
23 -
23 = 2 h
John's average speed
= 40 ÷ 2
= 20 km/h
Answer(s): (a) 06 10; (b) 20 km/h