A stream flows at 3 km/h. A boat can row 9 km/h in still water. How much time does it take to go 24 km downstream and return upstream to the starting point? MCQ with Answer and Explanation
A stream flows at 3 km/h. A boat can row 9 km/h in still water. How much time does it take to go 24 km downstream and return upstream to the starting point?
A. 6 hours
B. 8 hours
C. 7 hours
D. 5 hours
Answer: Option A
Solution (By JKSSB Mock Tests)
Downstream speed = 9 + 3 = 12 km/h. Upstream speed = 9 - 3 = 6 km/h. Time taken = 24/12 + 24/6 = 2 + 4 = 6 hours.
A thief is noticed by a policeman from a distance of 200 meters. The thief starts running and the policeman chases him. The thief and the policeman run at the rate of 10 km/h and 11 km/h respectively. What is the distance between them after 6 minutes?
Two cars A and B depart an intersection at the same time at right angles. A moves North at 36 km/h and B travels East at 48 km/h. Find the direct distance separating them after 30 minutes.
Explanation:
Time = 30 minutes = 0.5 hours. Distance covered by A = 36 * 0.5 = 18 km. Distance covered by B = 48 * 0.5 = 24 km. Direct distance = sqrt(18^2 + 24^2) = sqrt(324 + 576) = sqrt(900) = 30 km.
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