Mathmetics
ISBT Mathmetics for all banking PO,Clerk,IBPS PO,Railway,SSC,IAS,OAS Exams
Q61. 

1)  2  2)  4 
3)  6  4)  8 
5)  None of these 
Answer : 6
Explanation :
Explanation :
Let,speed of boat man be x kmph.
So, speed in down stream =(x+2) kmph. and speed in upstream = (x2) kmph.
Since, distance is constant for both case ,
the equation = 2(x2) = (x+2)
or 2x4 = x+2
or x= 6 kmph
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Q62. 

1)  456 km  2)  482 km 
3)  548 km  4)  552 km 
5)  None of these 
Answer : 552 km
Explanation :
Explanation :
Given, the first term, a = 35, common difference, d = 2 and total number of terms, (n) = 12.
The sum of this series will be the total distance travelled.
Sum, S_{n}= n/2[2a + (n  1) d] = 6 [70 + 11 x 2] = 552 km.
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Q63. 

1)  3  2)  5 
3)  9  4)  11 
5)  None of these 
Answer : 11
Explanation :
Explanation :
Let, the ten's digit be x and unit's digit be y.
Then, number = 10x + y.
Number obtained by interchanging the digits = 10y + x.
(10x + y) + (10y + x) = 11(x + y), which is divisible by 11.
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Q64. 

1)  Rs.800  2)  Rs.840 
3)  Rs. 880  4)  Rs.900 
5)  None of these 
Answer : Rs.900
Explanation :
Explanation :
Let, the price of the pen be ‘x’ and that of a pencil be ‘y’.
16x + 12y = 720 or (16x) X 5/4 + 12y X 5/4 = 720 X 5/4
or 20x + 15y = 900
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Q65. 

1)  3 : 2  2)  2 : 1 
3)  3 : 1  4)  4 : 3 
5)  None of these 
Answer : 2 : 1
Explanation :
Explanation :
Let, the number be ‘x’ and ‘y’
So, (x+y)/(xy) = 3/1
or x + y = 3x  3y
or 2x = 4y
or x:y = 2:1
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Q66. 

1)  184  2)  192 
3)  196  4)  212 
5)  None of these 
Answer : 192
Explanation :
Explanation :
(x + y)^{2} = (x  y)^{2} + 4xy
or x + y = 28, x  y = 4
or 4xy = (28)^{2}  (4)^{2}
or 4xy = (28 + 4) (28  4)
or xy = = 32 x 6 = 192
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Q67. 

1)  Rs.400  2)  Rs.500 
3)  Rs.600  4)  Rs.300 
5)  None of these 
Answer : Rs.300
Explanation :
Explanation :
Given, A + B + C = 1200
or A + B + 2C = 700 + 800 = 1500
or 1200  C + 2C = 1500
or C = 1500  1200 = 300
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Q68. 

1)  Rs.6500  2)  Rs. 7500 
3)  Rs.9000  4)  Rs.12000 
5)  None of these 
Answer : Rs. 7500
Explanation : Let, the man's income be Rs.x.
Explanation : Let, the man's income be Rs.x.
Expenditure on food = x/3 and expenditure on house rent = 2x/5
His saving = x  (x/3 + 2x/5) = 4x/15
So,4x/15 = 2000
or x =( 2000 X 15 ) /4 = 7500.
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Q69. 

1)  29 yrs  2)  35 yrs 
3)  31 yrs  4)  33 yrs 
5)  None of these 
Answer : 31 yrs
Explanation :
Explanation :
Let, the present ages of A and B be 2x years and 3x years respectively.
So, (2x4)/(3x4) = 5/8
or 16x  32 = 15x 20
or x = 12
Therefore, the Ages of A after 7 years = 2x + 7 = 2 x 12 + 7 = 31 years
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Q70. 

1)  9 days  2)  11 days 
3)  14 days  4)  12 days 
5)  None of these 
Answer : 12 days
Explanation :
Explanation :
3 men = 8 boys
2 m = (8/3)x2 = 16/3 boys.
(2 men + 6 boys) = (16/2)+6 boys = 34/3boys
8 boys can complete the work in 17 days
or 34/3boys boys can complete the work in x days
or (34/3) : 8 = 17 : x
or x =(17x8x3)/34 = 12 days
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