Luke took 6 hours to travel from Country Z to Country A at 60 km/h. Then he travelled from Country A to another country at 1.2 times his original speed. 70% of the distance from Country Z to Country A is equal to ¹₄ of the distance from Country A to the next country. Find the average speed for the whole journey and express it as a mixed number.
Distance he travelled from Country Z to Country A
= 6 x 60
= 360 km

Speed from Country A to another country
= 1.2 x 60
= 72 km/h

70% = ⁷⁰₁₀₀ = ⁷₆

⁷₁₀ Distance from Country Z to Country A = ¹₄ Distance from Country A to next country
⁷₁₀ Distance from Country Z to Country A = ⁷₂₈ Distance from Country A to next country

10 u = 360
1 u = 360 ÷ 10 = 36

Distance from Country A to the next country
= 28 u
= 28 x 36
= 1008 km

Time taken from Country A to the next country
= 1008 ÷ 72
= 14 h

Total distance of the whole journey
= 360 + 1008
= 1368 km

Total time taken for the whole journey = 6 + 14 = 20 h

Average speed of the whole journey
= 1368 ÷ 20
= 68 ⁸₂₀
= 68 ²₅ km/h

Answer(s): 68 ²₅ km/h