A person covers 35 km distance at the speed of 45 km/h, and after that he covers 95 km distance at the speed of 105 km/h. What is the average speed during the whole journey?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. .
Average Speed = Total Distance/Total Time
Total Distance = 35 km + 95 km = 130 km
Time for first 35 km at 45 km/h = 35/45 = 7/9 hours
Time for next 95 km at 105 km/h = 95/105 = 19/21 hours
Total Time = 9/7 + 19/21
⇒ Total Time = (49 + 57)/63 = 106/63 hours
Average Speed = (130)/(106/63) = 130 × 63/106 = (8190)/106 ≈ km/h