Jack took 6 hours to travel from Country D to Country E at 55 km/h. Then he travelled from Country E to another country at 1.2 times his original speed. 60% of the distance from Country D to Country E is equal to ¹₅ 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
= 6 x 55
= 330 km

Speed from Country E to another country
= 1.2 x 55
= 66 km/h

60% = ⁶⁰₁₀₀ = ³₆

³₅ Distance from Country D to Country E = ¹₅ Distance from Country E to next country
³₅ Distance from Country D to Country E = ³₁₅ Distance from Country E to next country

5 u = 330
1 u = 330 ÷ 5 = 66

Distance from Country E to the next country
= 15 u
= 15 x 66
= 990 km

Time taken from Country E to the next country
= 990 ÷ 66
= 15 h

Total distance of the whole journey
= 330 + 990
= 1320 km

Total time taken for the whole journey = 6 + 15 = 21 h

Average speed of the whole journey
= 1320 ÷ 21
= 62 ¹⁸₂₁
= 62 ⁶₇ km/h

Answer(s): 62 ⁶₇ km/h