A car covers a total distance of 360 km. It covers the first 120 km at 40 km/h. Of the remaining distance, it then covers one-third at 60 km/h and the rest at a constant speed v. If the car's overall average speed for the whole trip is 60 km/h, what is the value of v?
96 km/h
Total time for the trip \(= \dfrac{360}{60} = 6\) hours.
Time for the first 120 km \(= \dfrac{120}{40} = 3\) hours. Remaining distance = 240 km; one-third of it (80 km) at 60 km/h takes \(\dfrac{80}{60}=\dfrac{4}{3}\) hours.
Remaining distance = 160 km, remaining time \(= 6-3-\dfrac{4}{3}=\dfrac{5}{3}\) hours.
\(v = \dfrac{160}{5/3} = 96\) km/h.
Hence, this is the correct answer.(96 km/h) is correct.
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