Fred took 5 hours to travel from Country Q to Country R at 75 km/h. Then he travelled from Country R to another country at 1.2 times his original speed. 60% of the distance from Country Q to Country R is equal to ¹₆ of the distance from Country R to the next country. Find the average speed for the whole journey and express it as a mixed number.
Distance he travelled from Country Q to Country R
= 5 x 75
= 375 km

Speed from Country R to another country
= 1.2 x 75
= 90 km/h

60% = ⁶⁰₁₀₀ = ³₅

³₅ Distance from Country Q to Country R = ¹₆ Distance from Country R to next country
³₅ Distance from Country Q to Country R = ³₁₈ Distance from Country R to next country

5 u = 375
1 u = 375 ÷ 5 = 75

Distance from Country R to the next country
= 18 u
= 18 x 75
= 1350 km

Time taken from Country R to the next country
= 1350 ÷ 90
= 15 h

Total distance of the whole journey
= 375 + 1350
= 1725 km

Total time taken for the whole journey = 5 + 15 = 20 h

Average speed of the whole journey
= 1725 ÷ 20
= 86 ⁵₂₀
= 86 ¹₄ km/h

Answer(s): 86 ¹₄ km/h