Japheth drove from Town D to Town E which was 720 km away. He started from Town D at an average speed of 77 km/h. He maintained this speed for 4 h before increasing it by 6 km/h for the rest of the journey to Town E.
- How long did he take to complete the whole journey?
- What was his average speed from Town D to Town E?
(a)
Distance of 1st part of the journey
= 4 x 77
= 308 km
New speed for rest of the journey
= 77 + 6
= 83 km / h
Remaining distance for rest of the journey
= 720 - 308
= 412 km
Time taken for rest of the journey
= 412 ÷ 83
= 4 h
Total time taken
= 4 + 4
= 8 h
(b)
Average speed of the whole journey
= 720 ÷ 8
= 90 km
Answer(s): (a) 8 h; (b) 90km/h