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. 5 hours
B. 6 hours
C. 8 hours
D. 7 hours
Answer: Option B
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.
An airplane covers a certain distance at a speed of 240 km/h in 5 hours. To cover the same distance in 1 hour 40 minutes, it must travel at a speed of:
Explanation:
New speed = 5/6 of usual speed => New time = 6/5 of usual time. Difference = 1/5 of usual time = 15 minutes. Typical baseline time parameter = 15 * 5 = 75 minutes.
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