Kelsey travelled for 10 hours. He covered the first half of the distance at 25 kmph and remaining half of the distance at 40 kmph. Find the distance travelled by Kelsey?	Answers:
A) 583 km B) 400 km C) 670 km D) 360 km E) 234 km

Rationale: let the distance travelled be x km . total time = ( x / 2 ) / 25 + ( x / 2 ) / 40 = 10 = > x / 50 + x / 80 = 10 = > ( 8 x + 5 x ) / 400 = 10 = > x = 400 km answer : b
Answer: B