Warren took 6 hours to travel from Country Y to Country Z at 78 km/h. Then he travelled from Country Z to another country at 1.5 times his original speed. 25% 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
= 6 x 78
= 468 km

Speed from Country Z to another country
= 1.5 x 78
= 117 km/h

25% = ²⁵₁₀₀ = ¹₆

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

4 u = 468
1 u = 468 ÷ 4 = 117

Distance from Country Z to the next country
= 4 u
= 4 x 117
= 468 km

Time taken from Country Z to the next country
= 468 ÷ 117
= 4 h

Total distance of the whole journey
= 468 + 468
= 936 km

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

Average speed of the whole journey
= 936 ÷ 10
= 93 ⁶₁₀
= 93 ³₅ km/h

Answer(s): 93 ³₅ km/h