Justin took 4 hours to travel from Country J to Country K at 60 km/h. Then he travelled from Country K to another country at 1.3 times his original speed. 65% of the distance from Country J to Country K is equal to ¹₅ of the distance from Country K to the next country. Find the average speed for the whole journey and express it as a mixed number.
Distance he travelled from Country J to Country K
= 4 x 60
= 240 km

Speed from Country K to another country
= 1.3 x 60
= 78 km/h

65% = ⁶⁵₁₀₀ = ¹³₄

¹³₂₀ Distance from Country J to Country K = ¹₅ Distance from Country K to next country
¹³₂₀ Distance from Country J to Country K = ¹³₆₅ Distance from Country K to next country

20 u = 240
1 u = 240 ÷ 20 = 12

Distance from Country K to the next country
= 65 u
= 65 x 12
= 780 km

Time taken from Country K to the next country
= 780 ÷ 78
= 10 h

Total distance of the whole journey
= 240 + 780
= 1020 km

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

Average speed of the whole journey
= 1020 ÷ 14
= 72 ¹²₁₄
= 72 ⁶₇ km/h

Answer(s): 72 ⁶₇ km/h