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

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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Q82.  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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Q83.  Two numbers are such that their difference, their sum and their product are in the ratio 1:7:24 respectively. What is the product of the two numbers ? 
1)  12  2)  24 
3)  36  4)  48 
5)  None of these 
Answer : 48
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Q84.  The income of A,B and C together is Rs.14500 and they spend 60%,65% and 70% of their income respectively. If their savings are in the ratio 14:21:15 . What is the income of B ? 
1)  Rs.4000  2)  Rs.4800 
3)  Rs.5600  4)  Rs.6000 
5)  None of these 
Answer : Rs.6000
Explanation : We know that, income  expenditure = saving
Explanation : We know that, income  expenditure = saving
Let, their income are 100% individually.
So, A's saving = 100  60= 40% ; B's saving = 100  65= 35% ; C's saving = 100  70= 30%
But their saving ratio are 14:21:15.
Then, A's income , 40% = 14 or 100% =( 14/40) x 100 = 35
B's income , 35% = 21 or 100% =( 21/35) x 100 = 60
C's income , 30% = 15 or 100% =( 15/30) x 100 = 50
So, 35x + 60x + 50x = Rs.14500
or 145x = Rs.14500
or x = 100
Therefore income of B= 100x60 = Rs.6000.
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Q85. 

1)  1000  2)  1200 
3)  1400  4)  2000 
5)  None of these 
Answer : 1000
Explanation : Let, total numbers of students are x.
Explanation : Let, total numbers of students are x.
Girls = 3x/7. and boys = 1  3x/7 = 4x/7.
Below 10 years boys = (4x/7) 1/4 = 4x/28 = x/7
The girls are also below ten years of age = (3x/7) 5/6 = 5x/14
So, above ten years = x  (x/7 + 5x/14) = x x/2 = x/2
Given, x/2= 500
or x = 1000.
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Q86. 

1)  20 %  2)  24 % 
3)  25 %  4)  33.33 % 
5)  None of these 
Answer : 20 %
Explanation : Let, C.P of each article is Rs.1/.
Explanation : Let, C.P of each article is Rs.1/.
So, C.P of 20's articles = Rs.20/ and C.P of 4's articles = Rs.4/ i.e. profit
We know that, S.P = C.P + Profit = 20 + 4 = Rs. 24/
Therefore, % of profit = (4/20) x 100 = 20%
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Q87.  A vendor sells 20 articles and gets a profit which is equal to selling price of 4 articles. What is the percentage of profit in this transaction ? 
1)  20 %  2)  24 % 
3)  25 %  4)  33.33 % 
5)  None of these 
Answer : 25 %
Explanation : Let, S.P of each article is Rs.1/.
Explanation : Let, S.P of each article is Rs.1/.
So, S.P of 20's articles = Rs.20/ and S.P of 4's articles = Rs.4/ i.e. profit
We, know that C.P = S.P Profit = 20  4 = Rs. 16/
Therefore, % of profit = (4/16) x 100 = 25%
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Q88. 

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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Q89. 

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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Q90. 

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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