udaymathapati wrote:

A car traveling at a certain constant speed takes 2 seconds longer to travel 1 kilometer than it would take to travel 1 kilometer at 75 kilometers per hour. At what speed, in kilometers per hour, is the car traveling?

A. 71.5

B. 72

C. 72.5

D. 73

E. 73.5

If a car is traveling at 75 km per hour, then the number of seconds (x) it takes to travel 1 km can be calculated using the following proportion (note that 1 hour = 3,600 seconds):

75/3600 = 1/x

75x = 3600

x = 48 sec.

Thus, it takes 48 seconds to travel 1 km if the speed is 75 km/h. Since the car actually takes 2 more seconds (i.e., 50 seconds) to travel 1 km, its speed (r) can be calculated using the following proportion:

r/3600 = 1/50

50r = 3600

r = 72 km/h

Answer: B

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