Aptitude - Average - Discussion
Discussion Forum : Average - General Questions (Q.No. 15)
15.
A pupil's marks were wrongly entered as 83 instead of 63. Due to that the average marks for the class got increased by half (1/2). The number of pupils in the class is:
Answer: Option
Explanation:
Let there be x pupils in the class.
| Total increase in marks = |  |
x x | 1 |  |
= | x |
| 2 | 2 |
 |
x | = (83 - 63)  |
x | = 20 x= 40. |
| 2 | 2 |
Discussion:
123 comments Page 6 of 13.
Yash said:
7 years ago
@Nik.
Thanks for your explanation.
Thanks for your explanation.
Nelson said:
7 years ago
Let we take n be the number of students, x be the average of the students, so nx be the sum of observations,
(nx+20)/n=x+0.5,
nx+20=nx+0.5n,
0.5n=20, n=40.
(nx+20)/n=x+0.5,
nx+20=nx+0.5n,
0.5n=20, n=40.
Abhishek said:
8 years ago
@Utsav Sinha.
RHS should be;
X (y + 1/2y). Because average is increasing by half that means avg + 1/2 of avg.
RHS should be;
X (y + 1/2y). Because average is increasing by half that means avg + 1/2 of avg.
Abhishek Ojha said:
8 years ago
@Shubham.
In your case, You calculated Average Marks Not num of the pupil.
In your case, You calculated Average Marks Not num of the pupil.
Abhishek Ojha said:
8 years ago
@Deekshit.
It's INSUFFICIENT DATA.
63/n = 1/2 +av is incorrect . the correct one should be;
63/n = 1/2av + av : because av (average) is increased by half which means avg was changed to av + av/2 . And Most of the folks have done thia mistake only. Please ignore this question, there is Insufficient data to solve this.
It's INSUFFICIENT DATA.
63/n = 1/2 +av is incorrect . the correct one should be;
63/n = 1/2av + av : because av (average) is increased by half which means avg was changed to av + av/2 . And Most of the folks have done thia mistake only. Please ignore this question, there is Insufficient data to solve this.
Deekshith.D said:
8 years ago
1st condition : 83/n =av,
Here av is average.
2nd one is: 63/n = 1/2 +av,
So by solving these 2 eq. We have,
1/2 = 83/n - 63/n.
Solving this we will get n=2*20=40.
Here av is average.
2nd one is: 63/n = 1/2 +av,
So by solving these 2 eq. We have,
1/2 = 83/n - 63/n.
Solving this we will get n=2*20=40.
Shubham Singh said:
8 years ago
The simplest logic is;
If by increasing 20 marks(83-63) in the class the average increases by it's half = x+x/2.
Average of total marks = x
Average of total marks + 20 = x + x/2
Thus 20 = x/2;
=> x = 40.
If by increasing 20 marks(83-63) in the class the average increases by it's half = x+x/2.
Average of total marks = x
Average of total marks + 20 = x + x/2
Thus 20 = x/2;
=> x = 40.
Utsav Sinha said:
8 years ago
Simple logic.
Let no.of candidate = x.
Their average marks =y.
Generate an equation,
xy+83-63=x(y+1/2).
Solving we get y=40.
Let no.of candidate = x.
Their average marks =y.
Generate an equation,
xy+83-63=x(y+1/2).
Solving we get y=40.
Sharma said:
8 years ago
@Vishal explain it please.
7x/4y +2x/9y = 1/1.
we get 2:3.
7x/4y +2x/9y = 1/1.
we get 2:3.
MGM said:
8 years ago
How about this?
(83- 63)/ ? = 1/2
that is 20/ (1/2) = ?
Ans 40.
(83- 63)/ ? = 1/2
that is 20/ (1/2) = ?
Ans 40.
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers