1.
In a stream running at 2 km/h, a motor boat goes 10 km upstream and back again to the starting point in 55 min. Find the speed of the motorboat in still water.
• A.
20 km/h
• C.
24 km/h
• B.
22 km/h
• D.
21 km/h
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Explanation :
Let the speed of the motorboat in still water be x km/h

 10 x + 2
+
 10 x - 2
=
 55 60

 or, 240x = 11x2 - 44
 or, 11x2 - 240x - 44 = 0
(x - 22) (11x + 2) = 0
So, x = 2 km/h (neglecting the negative value)
Speed of the motorboat in still water = 22 km/h
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2.
A man can row 6 km/h in still water. If the river is running at 2 km/h, it takes 3 hours more in upstream than to go downstream for the same distance. How far is the place?
• A.
36 km
• C.
28 km
• B.
24 km
• D.
None of these
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Explanation :
The required distance =
 (x2 - y2)t 2y
=
 (36 - 4)3 2 x 2
= 24 km
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3.
Two boats, traveling 5 and 10 km/h, head directly towards each other. They begin at a distance of 20 kms from each other. How far apart are they (in kms) one minute before they collide?
• A.
1/3
• C.
1/4
• B.
1/6
• D.
1/12
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Explanation :
In the final one minute before collision, the two boats travel 5 x
 1 60
km and 10 x
 1 60
km i.e.,
 1 12

km and
 1 6
km, As they move in opposite directions, distance between the boats one minute before
collisions is
 1 12
+
 1 6
=
 1 4
km
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4.
A boat goes 13 km upstream in 39 minutes. The speed of stream is 3 km/h. The speed of boat in still water is
• A.
27 km/h
• C.
23 km/h
• B.
25 km/h
• D.
None of these
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Explanation :
Speed of the boat upstream =
 13 x 60 39
= 20 km/h
Speed of the stream = 3 km/h
Let the speed of the boat in still water = x km/h
We have, x � 3 = 20
x = 20 + 3 = 23 km/h
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5.
A motor went the river for 14 km and then up the river for 9 km. It took a total of 5 hours the entire journey. Find the speed of the river flow if the speed of the boat in still water is 5 km/h.
• A.
3 km/h
• C.
2 km/h
• B.
1.5 km/h
• D.
1 km/h
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