Valen took 6 hours to travel from Country R to Country S at 68 km/h. Then he travelled from Country S to another country at 1.5 times his original speed. 50% of the distance from Country R to Country S is equal to ¹₆ of the distance from Country S to the next country. Find the average speed for the whole journey and express it as a mixed number.
Distance he travelled from Country R to Country S
= 6 x 68
= 408 km

Speed from Country S to another country
= 1.5 x 68
= 102 km/h

50% = ⁵⁰₁₀₀ = ¹₆

¹₂ Distance from Country R to Country S = ¹₆ Distance from Country S to next country
¹₂ Distance from Country R to Country S = ¹₆ Distance from Country S to next country

2 u = 408
1 u = 408 ÷ 2 = 204

Distance from Country S to the next country
= 6 u
= 6 x 204
= 1224 km

Time taken from Country S to the next country
= 1224 ÷ 102
= 12 h

Total distance of the whole journey
= 408 + 1224
= 1632 km

Total time taken for the whole journey = 6 + 12 = 18 h

Average speed of the whole journey
= 1632 ÷ 18
= 90 ¹²₁₈
= 90 ²₃ km/h

Answer(s): 90 ²₃ km/h