Carl and Japheth 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, Carl cycled faster than Japheth. He arrived at the finishing point 40 minutes before Japheth who was 10 km behind him. Japheth did not change his speed throughout and completed it at 07 30.
- At what time did the trip begin? Give the answer in 12-hour format.
- What was Carl's average speed for the remaining 40 km of the trip in km/h?
(a)
60 min = 1 h
40 min =
4060 h =
23 Japheth's average speed
= 10 ÷
23 = 15 km/h
Time that Japheth took for the trip
= 50 ÷ 15
= 3
515 h
= 3
13 h
= 3 h 20 min
3 h 20 min before 07 30 is 04 10.
(b)
To find the time that Carl took for the remaining 40 km of the trip, we need to use the time that Japheth took subtract that of the time taken for first 10 km and the time that Carl was faster than Japheth.
Time that Carl took for the remaining 40 km of the trip
= 3
13 -
23 -
23 = 2 h
Carl's average speed
= 40 ÷ 2
= 20 km/h
Answer(s): (a) 04 10; (b) 20 km/h