If a car had traveled 25 kmh faster than it actually did, the trip would have lasted 30 minutes less. If the car went exactly 75 km, at what speed did it travel?  Choose the correct choice
A) 30 kmh
B) 40 kmh
C) 45 kmh
D) 50 kmh
E) 55 kmh

Rationale: time = distance / speed difference in time = 1 / 2 hrs 75 / x - 75 / ( x + 25 ) = 1 / 2 substitute the value of x from the options . - - > x = 50 - - > 75 / 50 - 75 / 75 = 3 / 2 - 1 = 1 / 2 answer : d
Answer: D