Japheth took 4 hours to travel from Country D to Country E at 75 km/h. Then he travelled from Country E to another country at 1.4 times his original speed. 70% of the distance from Country D to Country E is equal to ¹₆ of the distance from Country E to the next country. Find the average speed for the whole journey and express it as a mixed number.
Distance he travelled from Country D to Country E
= 4 x 75
= 300 km

Speed from Country E to another country
= 1.4 x 75
= 105 km/h

70% = ⁷⁰₁₀₀ = ⁷₄

⁷₁₀ Distance from Country D to Country E = ¹₆ Distance from Country E to next country
⁷₁₀ Distance from Country D to Country E = ⁷₄₂ Distance from Country E to next country

10 u = 300
1 u = 300 ÷ 10 = 30

Distance from Country E to the next country
= 42 u
= 42 x 30
= 1260 km

Time taken from Country E to the next country
= 1260 ÷ 105
= 12 h

Total distance of the whole journey
= 300 + 1260
= 1560 km

Total time taken for the whole journey = 4 + 12 = 16 h

Average speed of the whole journey
= 1560 ÷ 16
= 97 ⁸₁₆
= 97 ¹₂ km/h

Answer(s): 97 ¹₂ km/h