Oliver took 4 hours to travel from Country V to Country W at 54 km/h. Then he travelled from Country W to another country at 1.5 times his original speed. 25% of the distance from Country V to Country W is equal to ¹₆ of the distance from Country W to the next country. Find the average speed for the whole journey and express it as a mixed number.
Distance he travelled from Country V to Country W
= 4 x 54
= 216 km

Speed from Country W to another country
= 1.5 x 54
= 81 km/h

25% = ²⁵₁₀₀ = ¹₄

¹₄ Distance from Country V to Country W = ¹₆ Distance from Country W to next country
¹₄ Distance from Country V to Country W = ¹₆ Distance from Country W to next country

4 u = 216
1 u = 216 ÷ 4 = 54

Distance from Country W to the next country
= 6 u
= 6 x 54
= 324 km

Time taken from Country W to the next country
= 324 ÷ 81
= 4 h

Total distance of the whole journey
= 216 + 324
= 540 km

Total time taken for the whole journey = 4 + 4 = 8 h

Average speed of the whole journey
= 540 ÷ 8
= 67 ⁴₈
= 67 ¹₂ km/h

Answer(s): 67 ¹₂ km/h