Pierre took 4 hours to travel from Country M to Country N at 80 km/h. Then he travelled from Country N to another country at 1.4 times his original speed. 35% of the distance from Country M to Country N is equal to ¹₆ 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 80
= 320 km

Speed from Country N to another country
= 1.4 x 80
= 112 km/h

35% = ³⁵₁₀₀ = ⁷₄

⁷₂₀ Distance from Country M to Country N = ¹₆ Distance from Country N to next country
⁷₂₀ Distance from Country M to Country N = ⁷₄₂ Distance from Country N to next country

20 u = 320
1 u = 320 ÷ 20 = 16

Distance from Country N to the next country
= 42 u
= 42 x 16
= 672 km

Time taken from Country N to the next country
= 672 ÷ 112
= 6 h

Total distance of the whole journey
= 320 + 672
= 992 km

Total time taken for the whole journey = 4 + 6 = 10 h

Average speed of the whole journey
= 992 ÷ 10
= 99 ²₁₀
= 99 ¹₅ km/h

Answer(s): 99 ¹₅ km/h