Quantitative Aptitude: Average Questions Set 1

Averages Tricks Explanation for SBI PO, IBPS PO, NIACL, NICL, RBI Garde B, Dena Bank PO PGDBF, BOI, Bank of Baroda and other competitive exams.

1. The average of six numbers is 46. If a new number is added then the new average becomes 47. Find the new number?
   A) 47
   B) 52
   C) 54
   D) 53
   E) 55
   
   View Answer

   Option D
   Solution:
   basic method –
   6*46=X
   7*47=Y
   Y-X= ans
   Shortcut: 46+7= 53
   Because of New no, there is increase of 1 on each number. Now since there are 7 numbers, so 7*1 = 7 increment. So 46+7 = 53
2. The average age of 30 boys in a class is 15years. One boy aged 20yrs left the class, but the two new boy came in of his place, the difference of their ages was 5yrs.
   Now If the average age of all the boys in the class still remains 15yrs. Then find the age of the younger newcomer?
   A) 10yrs
   B) 20yrs
   C) 15yrs
   D) 8yrs
   E) 12yrs
   
   View Answer

   Option C
   Solution:
   one boy aged 20yrs left the class. If the total age was 30(15*2) of the two boys who came in, then there were no change in the average.
   But the boy left took away five more out of average. So now total = 30+5=35.
   X+X+5=35
   X=15.
3. If the average of 5 consecutive even number is 22. Then find the sum of largest and smallest number?
   A) 42
   B) 46
   C) 48
   D) 44
   E) 50
   
   View Answer

   Option D
   Solution:
   when odd number is given then keep average number in the middle.
   18 20 22 24 26
   Avg = 22
   Sum= 18+26= 44
4. The average of 6 consecutive even number is 43. Find the difference of largest & smallest number?
   A) 8
   B) 10
   C) 12
   D) 14
   E) 15
   
   View Answer

   Option B
   Solution:
   when even number is given in question, then the average lies in the middle of the two middle number .
   See here : 38 40 42 44 46 48
   43(average)
   Difference = 48-38= 10.
5. The average of a batsman in 19th innings is 49. He wants to make it 50 in his last innings. So how much score he has to make to make it 50?
   A) 64
   B) 79
   C) 69
   D) 59
   E) 73
   
   View Answer

   Option C
   Solution:
   basic method –
   19*49= X
   20*50=Y
   Y-X =Ans
   Shortcut:
   We have to make 49 to 50. means +1, This 1 will get added to each 20 innings. So 49 + 20 = 69
6. The average marks of 20 students in a class is 65. It is found that the marks of two students misread 35 instead of 53 and 48 instead of 84. Find the change in average after correction?
   A) 67
   B) 67.7
   C) 68
   D) 68.7
   E) 69
   
   View Answer

   Option B
   Solution:
   35+48= 83
   53+84=137
   54 more will be add and it change on 20 students
   54/20 = 2.7
   65+2.7 = 67.7
7. Find the average of first 20 multiple of 5?
   A) 52
   B) 53
   C) 52.5
   D) 53.5
   E) 51.5
   
   View Answer

   Option C
   Solution:
   first 20 multiple ……
   5,10,15,…………100.
   When difference is same then average = (1st term + last term)/2
   5+100/2 = 52.5
8. Find the average of 2²+4²+6²+8²…….+100²
   A) 3434
   B) 4343
   C) 4545
   D) 5454
   E) 3545
   
   View Answer

   Option A
   Solution:
   2²( 1²+2²+3²+…………..+50²)
   Average of n² = (n+1) (2n+1)/6
   [2² (50+1) ( 100+1) ]/6= 3434.
9. The average age of a couple is 25yrs. Find the new average age of them 4yrs after if a child was born 2year after their marriage ?
   A) 20
   B) 22
   C) 18
   D) 21
   E) 16
   
   View Answer

   Option A
   Solution:
   4yrs after the sum will be = 50+4+4+2 = 60
   50 is (25*2) . The second 4 is child’s age
   Average= 60/3 = 20
10. The average age of 19 students is 19. If the age of teacher is included the average become 20.Find the age of teacher?
    A) 35
    B) 37
    C) 39
    D) 42
    E) 45
    
    View Answer

    Option C
    Solution:
    19+20= 39