Peter took 5 hours to travel from Country A to Country B at 70 km/h. Then he travelled from Country B to another country at 1.2 times his original speed. 40% of the distance from Country A to Country B is equal to ¹₆ 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
= 5 x 70
= 350 km

Speed from Country B to another country
= 1.2 x 70
= 84 km/h

40% = ⁴⁰₁₀₀ = ²₅

²₅ Distance from Country A to Country B = ¹₆ Distance from Country B to next country
²₅ Distance from Country A to Country B = ²₁₂ Distance from Country B to next country

5 u = 350
1 u = 350 ÷ 5 = 70

Distance from Country B to the next country
= 12 u
= 12 x 70
= 840 km

Time taken from Country B to the next country
= 840 ÷ 84
= 10 h

Total distance of the whole journey
= 350 + 840
= 1190 km

Total time taken for the whole journey = 5 + 10 = 15 h

Average speed of the whole journey
= 1190 ÷ 15
= 79 ⁵₁₅
= 79 ¹₃ km/h

Answer(s): 79 ¹₃ km/h