A car traveling at a certain constant speed takes 30 seconds longer to travel 1 kilometer than it would take to travel 1 kilometer at 30 kilometers per hour. At what speed, in kilometers per hour, is the car traveling?
Choose the correct choice from the following.
A) 16
B) 18
C) 20
D) 22
E) 24

Rationale: "30 * t = 1 km = > t = 1 / 30 km / h v * ( t + 30 / 3600 ) = 1 v ( 1 / 30 + 30 / 3600 ) = 1 v ( 150 / 3600 ) = 1 v = 24 km / h the answer is e ."
Answer: E