Mathmetics
ISBT Mathmetics for all banking PO,Clerk,IBPS PO,Railway,SSC,IAS,OAS Exams
Q71. 

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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Q72. 

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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Q73. 

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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Q74. 

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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Q75. 

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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Q76. 

1)  38  2)  40 
3)  48  4)  56 
5)  None of these 
Answer : 40
Explanation :
Explanation :
Let, one number be x.
The other number = (88  x)
x x 3/10 = (88  x) x 36/100
= 30x = 3168  36x
x = 3168/66 = 48
The smaller number = 88  48 = 40
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Q77. 

1)  Rs. 210  2)  Rs. 130 
3)  Rs. 180  4)  Rs. 170 
5)  None of these 
Answer : Rs. 170
Explanation :
Explanation :
Let, the C.P. of 1 tube light be Rs.5x
C.P. of 1 bulb = Rs. 2x
4 x 5x + 3 x 2x = 260
x = 260/26 = 10
C.P. of 1 tube light and 6 bulbs
= 5 x X + 6 x 2 xX
= 5 x 10 + 12 x 10 = Rs.170
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Q78. 

1)  Rs.3200  2)  Rs.3126 
3)  Rs.3136  4)  Rs.3048 
5)  None of these 
Answer : Rs.3136
Explanation :
Explanation :
Let, the total amount of money with Alok be Rs.x .
x = (504 x 100)/[100  (23+33+19+16) ]= Rs. 5600
Reqd. amount of money
= ( Rs. 5600 x 56)/100= Rs. 3136
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Q79. 

1)  30 yrs  2)  24 yrs 
3)  18 yrs  4)  36 yrs 
5)  None of these 
Answer : 30 yrs
Explanation : The present age of Vijay = 72  42 = 30 years
Explanation : The present age of Vijay = 72  42 = 30 years
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Q80.  A some of money at compound interest amounts to thrice itself in three years. In how man years will it be nine times itself ? 
1)  4 years  2)  6 years 
3)  8 years  4)  12 years 
5)  None of these 
Answer : None of these
Explanation : Let, principal be x.It will be 3x after years.
Explanation : Let, principal be x.It will be 3x after years.
9x will takes another 3 years.
So,total time taken= 3+3 = 6 years.
Shortcut method:
x  3x in 3 years
9x i.e. (3x)^{2} = 3 X 2 = 6 years.
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