Japheth took 6 hours to travel from Country P to Country Q at 70 km/h. Then he travelled from Country Q to another country at 1.2 times his original speed. 60% of the distance from Country P to Country Q is equal to ¹₃ of the distance from Country Q to the next country. Find the average speed for the whole journey and express it as a mixed number.
Distance he travelled from Country P to Country Q
= 6 x 70
= 420 km

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

60% = ⁶⁰₁₀₀ = ³₆

³₅ Distance from Country P to Country Q = ¹₃ Distance from Country Q to next country
³₅ Distance from Country P to Country Q = ³₉ Distance from Country Q to next country

5 u = 420
1 u = 420 ÷ 5 = 84

Distance from Country Q to the next country
= 9 u
= 9 x 84
= 756 km

Time taken from Country Q to the next country
= 756 ÷ 84
= 9 h

Total distance of the whole journey
= 420 + 756
= 1176 km

Total time taken for the whole journey = 6 + 9 = 15 h

Average speed of the whole journey
= 1176 ÷ 15
= 78 ⁶₁₅
= 78 ²₅ km/h

Answer(s): 78 ²₅ km/h