A truck covers 60 km at 30 km/h and then another 100 km at 50 km/h. Find the overall average speed for the full transit. MCQ with Answer and Explanation
A truck covers 60 km at 30 km/h and then another 100 km at 50 km/h. Find the overall average speed for the full transit.
A. 38 km/h
B. 40 km/h
C. 45 km/h
D. 42 km/h
Answer: Option B
Solution (By JKSSB Mock Tests)
Total distance = 60 + 100 = 160 km. Time for first leg = 60 / 30 = 2 hours. Time for second leg = 100 / 50 = 2 hours. Total time = 4 hours. Average speed = 160 / 4 = 40 km/h.
A theft is reported at 4:00 AM. The thief runs at 50 km/h. The police begin chasing at 4:30 AM at 60 km/h. Find the distance from the starting point where the thief is caught.
Explanation:
In 30 minutes (0.5 hours), the thief covers 50 * 0.5 = 25 km. Relative speed = 60 - 50 = 10 km/h. Time taken to catch = 25 / 10 = 2.5 hours. Distance covered by police = 60 km/h * 2.5 hours = 150 km.
Explanation:
New speed = 7/8 of usual speed => New time = 8/7 of usual time. Difference = 1/7 of usual time = 10 minutes. Usual time = 10 * 7 = 70 minutes.
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