Justin took 6 hours to travel from Country V to Country W at 60 km/h. Then he travelled from Country W to another country at 1.5 times his original speed. 50% of the distance from Country V to Country W is equal to ¹₅ 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
= 6 x 60
= 360 km

Speed from Country W to another country
= 1.5 x 60
= 90 km/h

50% = ⁵⁰₁₀₀ = ¹₆

¹₂ Distance from Country V to Country W = ¹₅ Distance from Country W to next country
¹₂ Distance from Country V to Country W = ¹₅ Distance from Country W to next country

2 u = 360
1 u = 360 ÷ 2 = 180

Distance from Country W to the next country
= 5 u
= 5 x 180
= 900 km

Time taken from Country W to the next country
= 900 ÷ 90
= 10 h

Total distance of the whole journey
= 360 + 900
= 1260 km

Total time taken for the whole journey = 6 + 10 = 16 h

Average speed of the whole journey
= 1260 ÷ 16
= 78 ¹²₁₆
= 78 ³₄ km/h

Answer(s): 78 ³₄ km/h