Mathmetics
ISBT Mathmetics for all banking PO,Clerk,IBPS PO,Railway,SSC,IAS,OAS Exams
Q81. 

1)  24  2)  36 
3)  48  4)  72 
5)  None of these 
Answer : 48
Explanation : Let, the number be x.
Explanation : Let, the number be x.
So,x48 = x/3
or xx/3= 48
or x = 72
Therefore, twothirds of 72 is 48.
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Q82. 

1)  30  2)  40 
3)  50  4)  60 
5)  None of these 
Answer : 60
Explanation : Given, A’s marks in Arithmetic is x and A’s marks in English y and x +y=150  (I)
Explanation : Given, A’s marks in Arithmetic is x and A’s marks in English y and x +y=150  (I)
so, x/3 = y/2
or 2x =3y
or 2x  3y = 0  (II)
Putting the value in both equation, we get y = 60.
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Q83. 

1)  2525  2)  2925 
3)  3025  4)  3225 
5)  None of these 
Answer : 3025
Explanation : We know that , the sum of the cube all natural number i.e. 1 n = [(n. n+1)/2]^{2}
Explanation : We know that , the sum of the cube all natural number i.e. 1 n = [(n. n+1)/2]^{2}
The sequence is (1^{3} + 2^{3}+ 3^{3} + 4^{3}+ …….. + 10^{3})
So, [(10 x 11)/2]^{2} = 3025
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Q84. 

1)  2295  2)  2425 
3)  2595  4)  2925 
5)  None of these 
Answer : 2925
Explanation : We know that , the sum of the cube all natural number i.e. 1 n = [(n. n+1)/2]^{2}
Explanation : We know that , the sum of the cube all natural number i.e. 1 n = [(n. n+1)/2]^{2}
The sequence is (1^{3} + 2^{3}+ 3^{3} + 4^{3}+ …….. + 10^{3})  (1^{3} + 2^{3}+ 3^{3} + 4^{3})
So, [(10 x 11)/2]^{2}  [(4x5)/2]^{2} = 3025 100 = 2925
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Q85. 

1)  16  2)  52 
3)  58  4)  104 
5)  None of these 
Answer : 52
Explanation : Let, two numbers are x and y respectively.
Explanation : Let, two numbers are x and y respectively.
So, x^{2} + y^{2} = 68 and ( x  y )^{2} = 36.
We know that, ( x  y )^{2 }= x^{2} + y^{2}  2xy^{ }
or 68  2xy = 36
or 2xy = 68+36 = 104
or xy = 104/2=52
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Q86. 

1)  2  2)  3 
3)  4  4)  5 
5)  None of these 
Answer : 3
Explanation : Let, the number be x.
Explanation : Let, the number be x.
2x + 20 = 8x  4
or 8x  2x = 20 + 4 = 24
or 6x =24
or x= 24/6= 4
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Q87.  Threefourth of twothird of 240 is added to twothird of a number, the resultant number is 360. What is value of the original number ? 
1)  180  2)  240 
3)  320  4)  360 
5)  None of these 
Answer : 360
Explanation : Given , 3/4 x 2/3 x 240 +2x/3 = 360
Explanation : Given , 3/4 x 2/3 x 240 +2x/3 = 360
or 120 + 2x/3 = 360
or x = 360
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Q88. 

1)  625  2)  630 
3)  640  4)  650 
5)  None of these 
Answer : 625
Explanation : Short Cut Method:
Explanation : Short Cut Method:
Difference X (100)^{2}/ R^{2 }
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Q89. 

1)  1 km/hr.  2)  1.5 km/hr. 
3)  2 km/hr.  4)  3 km/hr. 
5)  None of these 
Answer : 1.5 km/hr.
Explanation :
Explanation :
Let, the speed of the stream be x km/hr.
Then, upward speed =(5 x)km/hr.
downward speed = (5 + x) km/hr.
So, (15/5+x) + (9/5x) = 5
or x = 2 km/hr
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Q90. 

1)  3 km/hr.  2)  4 km/hr. 
3)  6 km/hr.  4)  8 km/hr 
5)  None of these 
Answer : 3 km/hr.
Explanation :
Explanation :
Let, the speed of the stream be x km/hr.
Then, (91/10x) + (91/10+x) = 20
or x = 3 km./hr
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