Ken took 6 hours to travel from Country C to Country D at 75 km/h. Then he travelled from Country D to another country at 1.2 times his original speed. 60% of the distance from Country C to Country D is equal to ¹₆ of the distance from Country D to the next country. Find the average speed for the whole journey and express it as a mixed number.
Distance he travelled from Country C to Country D
= 6 x 75
= 450 km

Speed from Country D to another country
= 1.2 x 75
= 90 km/h

60% = ⁶⁰₁₀₀ = ³₆

³₅ Distance from Country C to Country D = ¹₆ Distance from Country D to next country
³₅ Distance from Country C to Country D = ³₁₈ Distance from Country D to next country

5 u = 450
1 u = 450 ÷ 5 = 90

Distance from Country D to the next country
= 18 u
= 18 x 90
= 1620 km

Time taken from Country D to the next country
= 1620 ÷ 90
= 18 h

Total distance of the whole journey
= 450 + 1620
= 2070 km

Total time taken for the whole journey = 6 + 18 = 24 h

Average speed of the whole journey
= 2070 ÷ 24
= 86 ⁶₂₄
= 86 ¹₄ km/h

Answer(s): 86 ¹₄ km/h