David took 5 hours to travel from Country G to Country H at 52 km/h. Then he travelled from Country H to another country at 1.5 times his original speed. 35% of the distance from Country G to Country H is equal to ¹₆ of the distance from Country H to the next country. Find the average speed for the whole journey and express it as a mixed number.
Distance he travelled from Country G to Country H
= 5 x 52
= 260 km

Speed from Country H to another country
= 1.5 x 52
= 78 km/h

35% = ³⁵₁₀₀ = ⁷₅

⁷₂₀ Distance from Country G to Country H = ¹₆ Distance from Country H to next country
⁷₂₀ Distance from Country G to Country H = ⁷₄₂ Distance from Country H to next country

20 u = 260
1 u = 260 ÷ 20 = 13

Distance from Country H to the next country
= 42 u
= 42 x 13
= 546 km

Time taken from Country H to the next country
= 546 ÷ 78
= 7 h

Total distance of the whole journey
= 260 + 546
= 806 km

Total time taken for the whole journey = 5 + 7 = 12 h

Average speed of the whole journey
= 806 ÷ 12
= 67 ²₁₂
= 67 ¹₆ km/h

Answer(s): 67 ¹₆ km/h