Oliver took 4 hours to travel from Country M to Country N at 65 km/h. Then he travelled from Country N to another country at 1.6 times his original speed. 40% of the distance from Country M to Country N is equal to ¹₅ of the distance from Country N to the next country. Find the average speed for the whole journey and express it as a mixed number.
Distance he travelled from Country M to Country N
= 4 x 65
= 260 km

Speed from Country N to another country
= 1.6 x 65
= 104 km/h

40% = ⁴⁰₁₀₀ = ²₄

²₅ Distance from Country M to Country N = ¹₅ Distance from Country N to next country
²₅ Distance from Country M to Country N = ²₁₀ Distance from Country N to next country

5 u = 260
1 u = 260 ÷ 5 = 52

Distance from Country N to the next country
= 10 u
= 10 x 52
= 520 km

Time taken from Country N to the next country
= 520 ÷ 104
= 5 h

Total distance of the whole journey
= 260 + 520
= 780 km

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

Average speed of the whole journey
= 780 ÷ 9
= 86 ⁶₉
= 86 ²₃ km/h

Answer(s): 86 ²₃ km/h