Dylan drove from Town Q to Town R which was 415 km away. He started from Town Q at an average speed of 78 km/h. He maintained this speed for 4 h before increasing it by 4 km/h for the rest of the journey to Town R.
- How long did he take to complete the whole journey?
- What was his average speed from Town Q to Town R?
(a)
Distance of 1st part of the journey
= 4 x 78
= 312 km
New speed for rest of the journey
= 78 + 4
= 82 km / h
Remaining distance for rest of the journey
= 415 - 312
= 103 km
Time taken for rest of the journey
= 103 ÷ 82
= 1 h
Total time taken
= 4 + 1
= 5 h
(b)
Average speed of the whole journey
= 415 ÷ 5
= 83 km
Answer(s): (a) 5 h; (b) 83km/h