The average velocity of the car for the whole journey is 69.57 km/h.
The given parameters:
The time spent by the before refueling is calculated as follows;
[tex]t = \frac{d}{v} \\\\t_1 = \frac{240}{75} \\\\t_1 = 3.2 \ hours[/tex]
The time spent by the car for the remaining journey;
[tex]t_3 = \frac{320 - 240}{100} \\\\t_3 = 0.8 \ hr[/tex]
The total time of the journey is calculated as follows;
[tex]t = t_1 + t_2 + t_3\\\\t = 3.2 \ hr \ + \ 0.6 \ hr \ + \ 0.8 \ hr\\\\t = 4.6 \ hours[/tex]
The average velocity of the car for the whole journey is calculated as follows;
[tex]v = \frac{total \ distance }{total \ time} \\\\v = \frac{320}{4.6} \\\\v = 69.57 \ km/h[/tex]
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