Julian took 4 hours to travel from Country Y to Country Z at 50 km/h. Then he travelled from Country Z to another country at 1.6 times his original speed. 50% of the distance from Country Y to Country Z is equal to ¹₄ of the distance from Country Z to the next country. Find the average speed for the whole journey and express it as a mixed number.
Distance he travelled from Country Y to Country Z
= 4 x 50
= 200 km

Speed from Country Z to another country
= 1.6 x 50
= 80 km/h

50% = ⁵⁰₁₀₀ = ¹₄

¹₂ Distance from Country Y to Country Z = ¹₄ Distance from Country Z to next country
¹₂ Distance from Country Y to Country Z = ¹₄ Distance from Country Z to next country

2 u = 200
1 u = 200 ÷ 2 = 100

Distance from Country Z to the next country
= 4 u
= 4 x 100
= 400 km

Time taken from Country Z to the next country
= 400 ÷ 80
= 5 h

Total distance of the whole journey
= 200 + 400
= 600 km

Total time taken for the whole journey = 4 + 5 = 9 h

Average speed of the whole journey
= 600 ÷ 9
= 66 ⁶₉
= 66 ²₃ km/h

Answer(s): 66 ²₃ km/h