David drove from Town M to Town N which was 546 km away. He started from Town M at an average speed of 65 km/h. He maintained this speed for 2 h before increasing it by 10 km/h for the rest of the journey to Town N.
- How long did he take to complete the whole journey?
- What was his average speed from Town M to Town N?
(a)
Distance of 1st part of the journey
= 2 x 65
= 130 km
New speed for rest of the journey
= 65 + 10
= 75 km / h
Remaining distance for rest of the journey
= 546 - 130
= 416 km
Time taken for rest of the journey
= 416 ÷ 75
= 5 h
Total time taken
= 2 + 5
= 7 h
(b)
Average speed of the whole journey
= 546 ÷ 7
= 78 km
Answer(s): (a) 7 h; (b) 78km/h