Mathmetics
ISBT Mathmetics for all banking PO,Clerk,IBPS PO,Railway,SSC,IAS,OAS Exams
Q1.  The batting average of 30 innings of a cricketer is 40 runs. His highest score exceeds his lowest score by 100 runs.If these two innings are not included, the average of the remaining 28 innings is 38. What is the lowest score of the player ? 
1)  12  2)  16 
3)  18  4)  20 
5)  None of these 
Answer : 18
Explanation : Let, the highest and lowest score are x and y respectively.
Explanation : Let, the highest and lowest score are x and y respectively.
So, x + y = (40 X 30 )  (28 X 38) = 136  (i)
Given, xy = 100  (ii)
Given, xy = 100
By solving, the above equation we get, x= 118 and x = 18
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Q2. 

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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Q3. 

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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Q4. 

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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Q5.  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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Q6. 

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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Q7. 

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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Q8. 

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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Q9. 

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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Q10. 

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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