A man complete a journey in 30 hours. He travels first half of the journey at the rate of 20 km/hr and second half at the rate of 10 km/hr. Find the total journey in km.  Choose the correct choice from the following choices.
A) 220 km  B) 224 km  C) 230 km  D) 400 km  E) 234 km

Rationale: 0.5 x / 20 + 0.5 x / 10 = 30 - - > x / 20 + x / 10 = 60 - - > 3 x = 20 x 60 - - > x = ( 60 x 20 ) / 3 = 400 km . answer : d
Answer: D