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The mean of 100 students marks was found to be 40. it was found later that a mark 53 was read as 83. the correct mean is? 
A) 40.30
B) 40.70
C) 39.40
D) 39.70
Correct Answer : 39.70 Explanation : As given, mean marks of 100 students = 40 
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The average salary of the entire staff in a office is 120 rs per month. The average salary of officers is 460 rs and that of non officers is 110 rs. If the number of officers is 15, then the number of non officers in the office is? 
A) 500
B) 488
C) 510
D) 450
Correct Answer : 510 Explanation : Let the required number of non officers = x 
Average of 11 numbers is 36, whereas average of 9 of them is 34. If the remaining two numbers are in the ratio 2:3, then find the value of the smallest number (between remaining two numbers) ? 
A) 36
B) 45
C) 48
D) 54
Correct Answer : 36 Explanation : Average = Sum of quantities/ Number of quantities Therefore,the numbers are 2x=>36 and 3x=>54 
The average age of 7 members of Patel's family is 25 year. The average age of the same family 3 year ago was? 
A) 21 year
B) 22 year
C) 25 year
D) 24 year
Correct Answer : 22 year Explanation : Present average age of family = 25 year 
The average salary of all the 60 employees in an office is Rs. 12,000 per month. if the number of executives is twice the number of non executives employees, then the average salary of all the non executives employees is ? 
A) Rs. 9000
B) Rs. 8000
C) Rs. 6000
D) Can't be determined
Correct Answer : Can't be determined Explanation : No. of executives / No. of non executives = 2 / 1 
The average age of a group of 10 friends is 15 yr. If one friend leaves the group, the average becomes 16 yr. Find the age of the friend who left the group ? 
A) 5 yr
B) 4 yr
C) 6 yr
D) 10 yr
Correct Answer : 6 yr Explanation : Age of friend left = Previous average of the age  Number of persons present x Increase in average age 
The average age of 24 students in a class is 10. If the teacher’s age is included, the average increase by one . The age of the teacher is ? 
A) 25 year
B) 30 year
C) 35 year
D) 40 year
Correct Answer : 35 year Explanation : Age of the teacher = Sum of age of 24 students and teacher  Sum of age of 24 students. 

The average marks of 30 students are 45 but after checking there are two mistakes found. After adjustment if a student got 45 more markes and other student got 15 less marks, then What will be the adjusted average? 
A) 45
B) 44
C) 47
D) 46
Correct Answer : 46 Explanation : Total number of all students of the class = 30 x 45 = 1350 After adjustment effective increment in marks=45–15=30 New total marks=1350+30=1380 Thus, New average after adjustment=1380/30=46 
The average weight of 60 students in a class was calculated to be 40 kg. Later it was found out that the weight of one of the students was calculated as 36 kg, whereas his actual weight was 33 kg. What is the actual average weight of the students in the class ? 
A) 39.90 kg
B) 39.95 kg
C) 39 kg
D) 38 kg
Correct Answer : 39.95 kg Explanation : Total correct weight = (40 x 60)  36 + 33 = 2400  3 = 2397 kg 
What is the average of the first 6 multiples of 7? 
A) 21
B) 28
C) 24.5
D) 25
Correct Answer : 24.5 Explanation : Required average =7*(1+2+3+4+5+6) / 6 

The average of 9 numbers is 18.If the average of first five numbers is 19 and the average of last 5 numbes is 17, find the 5th number? 
A) 16
B) 20
C) 18
D) 22
Correct Answer : 18 Explanation : Let x1, x2, x3, ......., x8, x9 be the numbers x1+ x2+ x3+ x4+ x5+ x6+ x7+ x8+ x9= 18*9 x1+ x2+ x3+ x4+ x5= 19*5 x5+ x6+ x7+ x8+ x9= 17*5 Adding equations (2) and (3) and then subtracting equation (1) from it, we get 
Five years ago the average age of four men is 48 years. Now, a new man joins and the average age increases by 2 years. What is the age of the new man? 
A) 36 years
B) 42 years
C) 41 years
D) 38 years
Correct Answer : 38 years Explanation : Sum of the ages of the four men five year ago= (48 *4) year = 192 year Now, a new man joins and the average age increases by 2 years = 48+2 =50 So, 50 =(212+ Age of the new man) / 5 
The mean yearly salary of employees of a company was 20000. The mean yearly salaries of male and female employees were 20800 and 16800 respectively. Find the ratio of males to females employed by the company? 
A) 3 : 2
B) 4 : 1
C) 2 : 1
D) 5 : 3
Correct Answer : 4 : 1 Explanation : Let the number of males be x and the number of females be y. 
Average of two numbers is 14.5 and square root of their product is 10. What are the numbers? 
A) 16 and 9
B) 25 and 4
C) 4 and 16
D) 25 and 9
Correct Answer : 25 and 4 Explanation : Let the number be a and b. Then Average is, (a +b) / 2 = 14.5 as given square root of their product is √ab = 10 (a  b)^{2} = (a + b)^{2}  4ab 
The average age of a group of four men whose ages are in the ratio 2: 3: 4: 5 is 42 years, what is the age of the eldest person in this group? 
A) 60 years
B) 48 years
C) 36 years
D) 24 years
Correct Answer : 60 years Explanation : Let the ages of the four men be 2x, 3x, 4x and 5x year respectively. 
If the mean of first n natural numbers is 13 then n=? 
A) 26
B) 25
C) 24
D) 20
Correct Answer : 25 Explanation : Sum of (1 + 2 + 3 +…. + n) =n(n+1)/2 Mean = [n(n+1)/2] / n => (n+1)/2 As given, (n+1)/2 = 13 
Find the median of the series: 38,28,34,42,50,40,48? 
A) 40
B) 48
C) 42
D) 28
Correct Answer : 40 Explanation : The median of a series of numbers is the number that appears in the middle . Median =40 Note:If the number of members of the series was even, the average of the two middle numbers would be the median 