A vehicle covers a total distance of 280 km. It finishes the first 120 km at 40 km/h and the remaining 160 km at 80 km/h. Find its average speed. MCQ with Answer and Explanation
A vehicle covers a total distance of 280 km. It finishes the first 120 km at 40 km/h and the remaining 160 km at 80 km/h. Find its average speed.
A. 52 km/h
B. 60 km/h
C. 64 km/h
D. 56 km/h
Answer: Option D
Solution (By JKSSB Mock Tests)
Time for first section = 120 / 40 = 3 hours. Time for second section = 160 / 80 = 2 hours. Total distance = 280 km, Total time = 5 hours. Average speed = 280 / 5 = 56 km/h.
A car driver leaves Bangalore at 8:30 AM and expects to reach a place 300 km away at 12:30 PM. At 10:30 AM he finds that he has covered only 40% of the distance. By how much must he increase the speed of the car to reach on scheduled time?
Explanation:
Total time available = 4 hours. At 10:30 AM (after 2 hours), distance covered = 40% of 300 = 120 km. Remaining distance = 180 km. Remaining time = 12:30 PM - 10:30 AM = 2 hours. Required speed = 180 / 2 = 90 km/h. Original speed = 120 / 2 = 60 km/h. Increase in speed = 90 - 60 = 30 km/h.
Explanation:
New speed = 7/9 of usual speed => New time = 9/7 of usual time. Difference = 2/7 of usual time = 12 minutes. 1/7 of usual time = 6 minutes => Usual time = 42 minutes.
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