When a train moves at an average speed of 100 kmph it reaches its destination on time. When its average speed becomes 80 kmph, then it reaches its destination 20 minutes late. Find the length of journey rounded to two decimal places.  Choices: A) 99.33 km B) 133.33 km C) 125.33 km D) 156.66 km E) none

Rationale: sol . difference between timings = 20 min = 1 / 3 hr . let the length of journey be x km . then , x / 80 - x / 100 = 1 / 3 â ‡ ” 5 x - 4 x = 133.33 â ‡ ” x = 133.33 km . answer b
Answer: B