Valen took 6 hours to travel from Country C to Country D at 70 km/h. Then he travelled from Country D to another country at 1.5 times his original speed. 50% of the distance from Country C to Country D is equal to ¹₅ 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 70
= 420 km

Speed from Country D to another country
= 1.5 x 70
= 105 km/h

50% = ⁵⁰₁₀₀ = ¹₆

¹₂ Distance from Country C to Country D = ¹₅ Distance from Country D to next country
¹₂ Distance from Country C to Country D = ¹₅ Distance from Country D to next country

2 u = 420
1 u = 420 ÷ 2 = 210

Distance from Country D to the next country
= 5 u
= 5 x 210
= 1050 km

Time taken from Country D to the next country
= 1050 ÷ 105
= 10 h

Total distance of the whole journey
= 420 + 1050
= 1470 km

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

Average speed of the whole journey
= 1470 ÷ 16
= 91 ¹⁴₁₆
= 91 ⁷₈ km/h

Answer(s): 91 ⁷₈ km/h