A motorboat rows 30 km downstream in 3 hours and tracks the identical route upstream back to the jetty point in 6 hours. Find the net speed index of the current stream flow. MCQ with Answer and Explanation
A motorboat rows 30 km downstream in 3 hours and tracks the identical route upstream back to the jetty point in 6 hours. Find the net speed index of the current stream flow.
A. 3.5 km/h
B. 2.5 km/h
C. 2.0 km/h
D. 3.0 km/h
Answer: Option B
Solution (By JKSSB Mock Tests)
Downstream speed = 30 / 3 = 10 km/h. Upstream speed = 30 / 6 = 5 km/h. Speed of current stream flow = (10 - 5) / 2 = 5 / 2 = 2.5 km/h.
The speeds of two bodies are in the ratio 5 : 6. If they clear the same sector distance, and the slower car takes 3 hours, how much time does the faster car take?
Explanation:
Ratio of speeds = 5:6, so ratio of times taken = 6:5. Slower car takes 6 parts = 3 hours => 1 part = 0.5 hours. Time for faster car = 5 parts = 5 * 0.5 = 2.5 hours.
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.
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