A motorist covers a distance of 39km in 45min by moving at a speed of x kmph for the first 15min, then moving at double the speed for the next 20 min, and then again moving at his original speed for the rest of the journey. Find x.  Choose the correct answer:  A) 29 kmph  B) 27 kmph  C) 55 kmph  D) 36 kmph  E) 29 kmph
36 kmph   36 kmph   Total distance = 39 km   Total time = 45 min   36 kmph = S*T   x * 15/60 + 2x * 20/60 + x * 10/60 = 39 km   x = 36 kmph
<result>D</result>
A motorist covers a distance of 39km in 45min by moving at a speed of x kmph for the first 15min, then moving at double the speed for the next 20 min, and then again moving at his original speed for the rest of the journey. Find x.