Luke took 3 hours to travel from Country B to Country C at 60 km/h. Then he travelled from Country C to another country at 1.2 times his original speed. 70% of the distance from Country B to Country C is equal to ¹₄ of the distance from Country C to the next country. Find the average speed for the whole journey and express it as a mixed number.
Distance he travelled from Country B to Country C
= 3 x 60
= 180 km

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

70% = ⁷⁰₁₀₀ = ⁷₃

⁷₁₀ Distance from Country B to Country C = ¹₄ Distance from Country C to next country
⁷₁₀ Distance from Country B to Country C = ⁷₂₈ Distance from Country C to next country

10 u = 180
1 u = 180 ÷ 10 = 18

Distance from Country C to the next country
= 28 u
= 28 x 18
= 504 km

Time taken from Country C to the next country
= 504 ÷ 72
= 7 h

Total distance of the whole journey
= 180 + 504
= 684 km

Total time taken for the whole journey = 3 + 7 = 10 h

Average speed of the whole journey
= 684 ÷ 10
= 68 ⁴₁₀
= 68 ²₅ km/h

Answer(s): 68 ²₅ km/h