RRB NTPC - Averages (200 Questions with Explanation): Quantitative Aptitude Test

41.

There were 20 students in a particular Class. The class teacher knows the overall height of all the students in the class is 1300. Can you find the average height of students in the class?

   A.) 65
   B.) 71.5
   C.) 68.25
   D.) 61.75

Answer: Option 'A'

Use the below formula to find the average height of students in the class Average Height = ( Total Height of all students in the Class / Total Number of Students) Average Height = ( 1300/20) = 65

42.

The average of 5 consecutive numbers is n. if the next two number are also included. The average will? 

   A.) Remain the same
   B.) Increase by 1
   C.) Increase by 2
   D.) Decrease by 1

Answer: Option 'B'

Increase by 1

43.

The average age of a group of 10 students was 24. The average age increased by 1 years when two new students joined the group. What is the average age of the two new students who joined the group? 

   A.) 30
   B.) 15.5
   C.) 19
   D.) 19.5

Answer: Option 'A'

The average age of a group of 10 students is 24
Therefore, the sum of the ages of all 10 of them
= 10 × 24
= 240
When two students joins the group, the average increase by 1
New Average = 25
Now there are 12 students.
Therefore, sum of all the ages of 12 students
= 12 × 25
300
Therefore, the sum of the ages of two students who joined
= 300 - 240
= 60
And the average age of these two students
= 60 / 2
30.

44.

Six years ago, the ratio of the ages of Kunal and Sagar was 6 : 5. Four years hence, the ratio of their ages will be 11 : 10. What is Sagar's age at present?  

   A.) 16 years
   B.) 20 years
   C.) 18 years
   D.) Cannot be determined

Answer: Option 'A'

Given, Six years ago, the ratio of ages ofKunal and Sagar = 6 : 5
Thus, the ages of Kunal and Sagar 6 years ago be 6x and 5x years respectively.
Then, the present age of Kunal = 6x + 6
the present age of Sagar = 5x + 6
Given,Four years hence, the ratio of their ages will be 11 : 10
=> The age of Kunal after four years = 6x + 6 + 4 = 6x + 10
The age of Sagar after four years = 5x + 6 + 4 = 5x + 10
=>(6x + 10) / (5x + 10) = 11 / 10
=> 10 (6x + 10) = 11 (5x + 10)
=> 60x + 100 = 55x + 110
=> 60x - 55x = 110 - 100
=> 5x = 10
=> x = 2
Thus, present age of Sagar =5x + 6
= 5(2) + 6
= 10 + 6
16 years

45.

There were 45 students in a hostel, if the numbers of students increased by 7, the expenses of the mess were increased by Rs. 39 per day while the average expenditure per head diminished by Re.1. What is the original expenditure of the mess? 

   A.) Rs. 562
   B.) Rs. 624
   C.) Rs. 1950
   D.) Rs. 585

Answer: Option 'D'

Let the original expenditure be Rs.x
Original average expenditure = X/45
New average expenditure = (x+39)/52
So (x/45) - ((x+39) / 52) = 1  so x = 585
so, original expenditure is Rs 585

46.

Of three numbers, the third is twice the second and the second is 4 times the first. If their average is 78, the smallest of the three numbers is: 

   A.) 15
   B.) 21
   C.) 17
   D.) 18

Answer: Option 'D'

Let first number be x. 
So,2nd no. = 4x & 3rd no.=8x.
So,x+4x+8x=78 × 3 = 234.
13x = 234 
x = 234/13 
Hence,smallest Number x=18.

47.

The average of marks of a student of 8 exams was 35. How many marks must be get in the next exam so as to increase his average of marks by 5?

   A.) 75
   B.) 80
   C.) 83
   D.) 79

Answer: Option 'B'

80

48.

The average weight of a class having 16 students is 36 kg. Find the total weight of the class.

   A.) 576
   B.) 526
   C.) 496
   D.) 556

Answer: Option 'A'

Solution is :
Given, average weight = 36 kg
No. of students = 16
Average = Total Quantity / No. of Quantity
=> Total weight of the class = Average weight x No. of Students
= 36 × 16
= 576 kg

49.

Average of five consecutive even numbers is 35. Find the greatest number in these five numbers? 

   A.) 31
   B.) 33
   C.) 39
   D.) 36

Answer: Option 'C'

39

50.

There were 22 students in a particular Class. The class teacher knows the overall height of all the students in the class is 1300. Can you find the average height of students in the class?

   A.) 56.14
   B.) 62.04
   C.) 65
   D.) 59.09

Answer: Option 'D'

Use the below formula to find the average height of students in the class Average Height = ( Total Height of all students in the Class / Total Number of Students) Average Height = ( 1300/22) = 59.09

51.

In the first 25 overs of a cricket game, the run rate was only 1.3. What should be the run rate in the remaining 25 overs to reach the target of 287 runs?

   A.) 10.18
   B.) 9.162
   C.) 12.216
   D.) 14.058

Answer: Option 'A'

Required Run rate = ( 287 - ( 1.3 x 25 ) )/ (25) = ( 254.5) /(25) = 10.18

52.

Total Marks obtained by a class is 1872 and the average score of the class is 72. Find the Total students in the class?

   A.) 27
   B.) 26
   C.) 25
   D.) 24

Answer: Option 'B'

Use the below formula to find the Total, when Average and Total No. of Students is provided Total no of students = Total Marks / Average Marks Total No. of students = ( 1872 / 72) = 26

53.

The average of 26 numbers is zero. Of them, at the most how many may be greater than zero?

   A.) 25
   B.) 27
   C.) 24
   D.) 13

Answer: Option 'A'

Average of 26 numbers is = 0 Therefore sum of all 26 numbers = 0
It is quite possible that 25 of these numbers may be positive and if their sum is "a" then 26th number is "(-a)"

54.

The average of 12 numbers is 24. If each number be multiplied by 6. Find the average of new set of numbers?

   A.) 48
   B.) 144
   C.) 65
   D.) 121

Answer: Option 'B'

New Average = Old Average x 6 = 24 x 6 = 144

55.

 In a class of 18 students in an examination in science 1 student scored 100 marks, 2 get zero each and the average oh the rest was 45. What is the average of the whole class? 

   A.) 41
   B.) 43
   C.) 42
   D.) 44

Answer: Option 'B'

43

56.

The average age of a group of 10 students was 14. The average age increased by 1 years when two new students joined the group. What is the average age of the two new students who joined the group?

   A.) 20
   B.) 20.5
   C.) 21.5
   D.) 19

Answer: Option 'A'

The average age of a group of 10 students is 14.
Therefore, the sum of the ages of all 10 of them = 10 * 14 = 140
When two students joins the group, the average increase by 1. New Average = 15
Now there are 12 students
Therefore, sum of all the ages of 12 students = ( 12 X 15 ) = 180
Therefore, the sum of the ages of two students who joined = 180 - 140 = 40
And the average age of these two students =20

57.

The average age of a group of 10 students was 26. The average age increased by 1 years when two new students joined the group. What is the average age of the two new students who joined the group ?

   A.) 20
   B.) 16.5
   C.) 18.5
   D.) 21.5

Answer: Option 'C'

The average age of a group of 10 students is 26.
Therefore, the sum of the ages of all 10 of them = 10 × 26 = 260
When two students joins the group, the average increase by 1.
New Average = 27 Now there are 11 students
Therefore, sum of all the ages of 11 students = 297
Therefore, the sum of the ages of two students who joined = 297 - 260 = 37
And the average age of these two students = 18.5

58.

A is two years older than B who is twice as old as C. If the total of the ages of A, B and C be 27, then how old is B? 

   A.) 7
   B.) 9
   C.) 10
   D.) 8

Answer: Option 'C'

Given
Let C's age be x years.
Then, B's age = 2x years.
A's age = (2x + 2) years.
(2x + 2) + 2x + x = 27
5x = 25
x = 5.
Hence, B's age
= 2x
= 2 × 5
= 10 years.

59.

Physics Teacher knows the average score of 33 students in her subject is 49.5. Can you help the physics teacher to find the overall marks obtained by all the students in her subject?

   A.) 1551.83
   B.) 1633.5
   C.) 1796.85
   D.) 1726.85

Answer: Option 'B'

Use the below formula to find the Total, when Average and Total No. of Students is provided Total = Average * Total Students/People Total = Average * Total Number of Students) Average Weight = ( 49.5 x 33) = 1633.5

60.

There were 8 students in a particular Class. The class teacher knows the overall height of all the students in the class is 1400. Can you find the average height of students in the class?

   A.) 192.5
   B.) 175
   C.) 183.75
   D.) 166.25

Answer: Option 'B'

Use the below formula to find the average height of students in the class Average Height = ( Total Height of all students in the Class / Total Number of Students) Average Height = ( 1400/8) = 175


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