Mathmetics
ISBT Mathmetics for all banking PO,Clerk,IBPS PO,Railway,SSC,IAS,OAS Exams
Q521.  A man takes twice as long to row a distance against the stream as to row the same distance in favour of the stream. The ratio of the speed of the boat (in still water) and the stream is: 
1)  2:1  2)  3:2 
3)  2:3  4)  3:1 
5)  None of these 
Answer : 3:1
Explanation :
Explanation :
Let man's rate upstream be x kmph.
Then, his rate downstream = 2x kmph.
(Speed in still water) : (Speed of stream) = (2x+2) /2 : (2xx)/2
=3x/2: x/2 = 3 : 1.
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Q522.  A boat covers a certain distance downstream in 1 hour, while it comes back in 1 hours. If the speed of the stream be 3 kmph, what is the speed of the boat in still water ? 
1)  10kmph  2)  12kmph 
3)  15kmph  4)  18kmph 
5)  None of these 
Answer : 15kmph
Explanation :
Explanation :
Let the speed of the boat in still water
be x kmph. Then,
Speed downstream = (x + 3) kmph,
Speed upstream = (x  3) kmph.
(x
+ 3) x 1 = (x  3)/2 x3
Or 2x + 6 = 3x  9
Or x = 15 kmph.
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Q523.  A man can row at 5 kmph in still water. If the velocity of current is 1 kmph and it takes him 1 hour to row to a place and come back, how far is the place ? 
1)  2.4 km  2)  2.5km 
3)  3km  4)  3.6km 
Answer : 2.4 km
Explanation :
Explanation :
Speed downstream = (5 + 1) kmph = 6 kmph.
Speed upstream = (5  1) kmph = 4 kmph.
Let the required distance be x km.
Then,x/6 +x/4 = 1
Or
2x + 3x = 12
Or 5x = 12
Or x = 2.4 km.
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Q524. 

1)  4  2)  5 
3)  6  4)  10 
5)  None of these 
Answer : 5
Explanation :
Explanation :
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Q525.  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: 
1)  7.5 km/hr  2)  8.5 km/hr 
3)  10 km/hr  4)  12.5 km/hr 
5)  None of these 
Answer : 10 km/hr
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Q526. 

1)  3 km/hr  2)  5 km/hr 
3)  8 km/hr  4)  9 km/hr 
5)  None of these 
Answer : 8 km/hr
Explanation : Speed in still water = ½(11 + 5) kmph = 8 kmph.
Explanation : Speed in still water = ½(11 + 5) kmph = 8 kmph.
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Q527. 

1)  8.5 km/hr  2)  9 km/hr 
3)  10 km/hr  4)  12.5 km/hr 
5)  None of these 
Answer : 10 km/hr
Explanation :
Explanation :
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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Q528. 

1)  2 hours  2)  3 hours 
3)  4 hours  4)  5 hours 
5)  None of these 
Answer : 4 hours
Explanation :
Explanation :
Speed downstream = (13 + 4) km/hr = 17 km/hr.
Time taken to travel 68 km downstream = ( 68/17) hrs = 4 hrs.
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Q529. 

1)  20 km/hr  2)  22 km/hr 
3)  24 km/hr  4)  28 km/hr 
5)  None of these 
Answer : 22 km/hr
Explanation :
Explanation :
Let the speed of the man in still water be x km/hr. then,
km/hr.
10/(x2) + 10/(x+2) = 55/60
or x = 22 km/hr
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Q530. 

1)  17 kg  2)  20 kg 
3)  26 kg  4)  31 kg 
5)  None of these 
Answer : 31 kg
Explanation :
Explanation :
Let A, B, C represent their respective weights. Then, we have:
A + B + C = (45 x 3) = 135 .... (i)
A + B = (40 x 2) = 80 .... (ii)
B + C = (43 x 2) = 86 ....(iii)
Adding (ii) and (iii), we get: A + 2B + C = 166 .... (iv)
Subtracting (i) from (iv), we get : B = 31.
B's weight = 31 kg.
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