Mathmetics

ISBT Mathmetics for all banking PO,Clerk,IBPS PO,Railway,SSC,IAS,OAS Exams

Q551.
35% of a number is 175. What % of 175 is the number ?
1) 285.71% 2) 283.71%
3) 289.91% 4) 285.71%
5)None of these
Answer : 285.71%
Explanation : Let ‘x’ be the number 
(35/100)x = 175
or  x= (175 x 100)/35
So,required percentage = (500/75)/100 =  285.71%


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Q552.
A candidate scoring 25% in an examination fails by 30 marks while another candidate who scores 50% marks gets 20 marks more than the minimum required for a pass. Find the full mark in the examination ?
1) 200 2) 240
3) 240 4) 500
5)None of these
Answer : 200
Explanation :
Let, the full mark be x.
The first candidate's pass mark = (25/100)x +30
The second candidate's pass mark = ( 50/100 )x-20
So,  (25/100)x +30 = ( 50/100 )x-20
       Or x= 200
Shortcut  Method :
             Full-Mark = (Diff. in marks / diff.in %) x 100
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Q553.
In an election between two candidates, one got 55% of the total valid votes, 20% of the votes were invalid. If the total number of votes was 7500, the number of valid votes that the other candidate got, was:
1) 2500 2) 2600
3) 2700 4) 3000
5)None of these
Answer : 2700
Explanation :

Number of valid votes = 80% of 7500 = 6000.

So, Valid votes polled by other candidate = 45% of 6000

= (45/100 x 6000 = 2700.

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Q554.
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 :

Let man's rate upstream be x kmph.

Then, his rate downstream = 2x kmph.

 (Speed in still water) : (Speed of stream) = (2x+2) /2 : (2x-x)/2

   =3x/2: x/2 = 3 : 1.

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Q555.
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 :

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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Q556.
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 :

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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Q557.
A motorboat, whose speed in 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream (in km/hr) is:

1) 4 2) 5
3) 6 4) 10
5)None of these
Answer : 5
Explanation :



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Q558.
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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Q559.
n 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:
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.
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Q560.
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) 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 :
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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