Mathmetics
ISBT Mathmetics for all banking PO,Clerk,IBPS PO,Railway,SSC,IAS,OAS Exams
Q1. 

1)  Rs.1650  2)  Rs.2000 
3)  Rs.2400  4)  Rs.3500 
5)  None of these 
Answer : Rs.1650
Explanation :
Explanation :
Shortcut Method :
(Final Strength X Increases Value) + earlier average
i.e. ( 17 X 50) + 800 = Rs. 1650
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Q2. 

1)  17 years  2)  18 years 
3)  19 years  4)  20 years 
5)  None of these 
Answer : 19 years
Explanation : The total age of 50 students = 50 X 16 = 800 yrs.
Explanation : The total age of 50 students = 50 X 16 = 800 yrs.
After admitted 10 new students ,total age become 60 X 16.5 = 990 yrs.
So, age of new students = 990 800 = 190 yrs.
Thus, their average 190 /10 = 19 yrs.
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Q3. 

1)  Rs.5,425  2)  Rs.5,500 
3)  Rs.5,446  4)  Rs.5,600 
5)  None of these 
Answer : Rs.5,425
Explanation :
Explanation :
Total expenditure is = (55000 + 75400) = 62800
His saving is Rs. 2300
Total annual income = 62800 + 2300 = 65100
Monthly income = 65100 ÷ 12 = Rs. 5425
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Q4.  There are some adult students in a class and their average age was 40 years. If 12 new students with an average age of 50 years join with them, their new average age will be increases by 5 years.What was the original strength of that class ? 
1)  8  2)  10 
3)  12  4)  15 
5)  None of these 
Answer : 12
Explanation : Let, there were x number of students in the class.
Explanation : Let, there were x number of students in the class.
Given that their average age was 40 yrs.
So, their total age was = 40x yrs
Now, 12 new students join with them with an average age of 50 yrs.
Then, total age was = (12 x 50) = 600 yrs. and total students were x+12.
Now, new total age was = (4x + 600 ) yrs.
So, (40x + 600 ) / (x+12) = 45
or 45x + 540 = 40x + 600
or 5x = 600 540 = 60
or x = 60/5 = 12
Thus, original strength of that class was 12.
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Q5. 

1)  39 years  2)  40 years 
3)  44 years  4)  Data Inadequate 
5)  None of these 
Answer : 39 years
Explanation :
Explanation :
When the teacher is included there are totally 31 members in the class and the average is increased by 1 year. This means that everyone got 1 extra year after distributing the extra years of the teacher.
So, extra years of the teacher are as follow: 31Ã—1=31 years.
Age of the teacher = actual avg + extra years = 12 + 31 = 43 years
Age of the teacher = (25 x 15  24 x 14) = 39 years.
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Q6. 

1)  Rs.400  2)  Rs.432 
3)  Rs.442  4)  Rs.420 
5)  None of these 
Answer : Rs.420
Explanation : Let, the average expenditure of the mess per day is Rs.x.
Explanation : Let, the average expenditure of the mess per day is Rs.x.
Then, total expenditure/day = Rs.35x
Now, total students = 35+7= 42 and new expenditure of the mess = Rs.(35x +42)
So, Rs.(35x +42) /42 = Rs.x1
or 35x + 42 = 42x 42
or 7x = 84
or x = 12
Therefore, original expenditure of the mess = 35 x 12= Rs.420
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Q7. 

1)  8  2)  10 
3)  11  4)  14 
5)  None of these 
Answer : 11
Explanation :
Explanation :
Let, the number of subjects = x
Then, Total marks he scored for all subjects = 63x
If he had obtained 20 more marks for his mathematics and 2 more marks for his geography, his average would have been 65.
=> Total marks he would have scored for all subjects = 65x
Now, we can form the equation as 65x  63x = the additional marks of the student
= 20 + 2 = 22
=> 2x = 22
=>x=22/2=11
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Q8. 

1)  62  2)  64 
3)  66  4)  72 
5)  None of these 
Answer : 66
Explanation :
Explanation :
Let, the average up to 15th innings = x.
Total runs scored in 15 innings = 15x
Then average after 16 innings = (x+2).
Total runs scored in 16 innings = (15x + 96)
So, (15x + 96)/16 = (x+2)
=> 15x + 96 = 16x + 32
=> x = 64
Therefore, his average run after 16th innings is 64+2= 66 runs.
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Q9. 

1)  75 Kg  2)  65 Kg 
3)  80 Kg  4)  85 Kg 
5)  None of these 
Answer : 75 Kg
Explanation :
Explanation :
Total increase in weight = 10×3 = 30
If x is the weight of the new person, total increase in weight = x  45
=> 30 = x  45
=> x = 30 + 45 = 75 kg
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Q10. 

1)  42  2)  48 
3)  50  4)  52 
5)  None of these 
Answer : 48
Explanation : Let, the average run up to 10 innings is X.
Explanation : Let, the average run up to 10 innings is X.
So, total run =10X.
Now, after 11th innings ,the total run = 10X + 108 .
The new new average =(10X + 108) /11 . So, the equation = (10X + 108) /11 =X +6 or X= 42
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