An ocean current flows at a rate of 1.5 km/hr. A shark can swim in still water at the rate 4.5 km/hr. What is the average speed for the entire distance travelled, if the shark swims from India to Australia and comes back?
Answer: B
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A man's speed with the current is 15 km/hr and the speed of the current is 2.5 km/hr. The man's speed against the current is:
Answer: C
Man's rate in still water = (15 - 2.5) km/hr = 12.5 km/hr.
Man's rate against the current = (12.5 - 2.5) km/hr = 10 km/hr.
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If Rahul rows 15 km upstream in 3 hours and 21 km downstream in 3 hours, then the speed of the stream is
Answer: D
Rate upstream = (15/3) kmph
Rate downstream (21/3) kmph = 7 kmph
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Speed of stream (1/2)(7 - 5)kmph = 1 kmph
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A boat can travel with a speed of 13 km/hr in still water. If the speed of the stream is 4 km/hr, find the time taken by the boat to go 68 km downstream.
Answer: C
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A man can row 6 kmph in still water. When the river is running at 1.2 kmph, it takes him 1 hour to row to a place and black. How far is the place?
Answer: B
M = 6
S = 1.2
DS = 6 + 1.2 = 7.2
US = 6 - 1.2 = 4.8
x/7.2 + x/4.8 = 1
x = 2.88
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In one hour, a boat goes 11 km/hr along the stream and 5 km/hr against the stream. The speed of the boat in still water (in km/hr) is:
Answer: C
Speed in still water = 1/2(11 + 5) kmph = 8 kmph.
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A man can row downstream at 18 kmph and upstream at 10 kmph. Find the speed of the man in still water and the speed of stream respectively?
Answer: D
Let the speed of the man in still water and speed of stream be x kmph and y kmph respectively.
Given x + y = 18 --- (1)
and x - y = 10 --- (2)
From (1) & (2) 2x = 28 => x = 14, y = 4.
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A boat goes 24 km downstream in 10 hours, it takes 2 hours more to cover the same distance against the stream. What is the speed of the boat in still water?
Answer: D
Speed downstream = 24/10 km/hr = 2.4 km/hr
Speed upstream = 24/12 km/hr = 2 km/hr
Speed of the boat in still water = ½ (2.4 +2)km/hr = 2.2 km/hr
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The speed of a boat in still water is 5 km/hr, it can go 30km upstream and return downstream to the original point in 4 hours 30 min. The speed of the stream is?
Answer: A
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A boat running downstream covers a distance of 20 km in 2 hours while for covering the same distance upstream, it takes 5 hours. What is the speed of the boat in still water?
Answer: B
Rate downstream = (20/2) kmph = 10 kmph;
Rate upstream = (20/5) kmph = 4 kmph
Speed in still water = 1/2 (10 + 4) kmph = 7 kmph
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