Fred took 4 hours to travel from Country A to Country B at 80 km/h. Then he travelled from Country B to another country at 1.4 times his original speed. 70% of the distance from Country A to Country B is equal to ¹₅ of the distance from Country B to the next country. Find the average speed for the whole journey and express it as a mixed number.
Distance he travelled from Country A to Country B
= 4 x 80
= 320 km

Speed from Country B to another country
= 1.4 x 80
= 112 km/h

70% = ⁷⁰₁₀₀ = ⁷₄

⁷₁₀ Distance from Country A to Country B = ¹₅ Distance from Country B to next country
⁷₁₀ Distance from Country A to Country B = ⁷₃₅ Distance from Country B to next country

10 u = 320
1 u = 320 ÷ 10 = 32

Distance from Country B to the next country
= 35 u
= 35 x 32
= 1120 km

Time taken from Country B to the next country
= 1120 ÷ 112
= 10 h

Total distance of the whole journey
= 320 + 1120
= 1440 km

Total time taken for the whole journey = 4 + 10 = 14 h

Average speed of the whole journey
= 1440 ÷ 14
= 102 ¹²₁₄
= 102 ⁶₇ km/h

Answer(s): 102 ⁶₇ km/h