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 11 of 13.
Ash said:
1 decade ago
Karthy is right....
Sowjanya said:
1 decade ago
If solution A which has milk to water in the ratio 7:4 is mixed with solution B which has the ratio of water to milk as 9:2 such that the ratio becomes 1:1, then in what ratio were they mixed?
A) 2:3 B) 7:3 C) 1:1 D) 3:4.
Please solve this.
A) 2:3 B) 7:3 C) 1:1 D) 3:4.
Please solve this.
Adnan said:
1 decade ago
Let avg=y, no. of pupils=x, sum of marks=s
Case 1) y= s/x -------------(i)
Case 2) y + 1/2= (s+20)/x ----------(ii)
Solving eq. i & ii gives,x=40
Case 1) y= s/x -------------(i)
Case 2) y + 1/2= (s+20)/x ----------(ii)
Solving eq. i & ii gives,x=40
Karthy said:
1 decade ago
The average increase for one person is 0.5
Total increase is 20
Therefore Total no of pupil =20/0.5 = 40.
Total increase is 20
Therefore Total no of pupil =20/0.5 = 40.
(2)
Rav said:
1 decade ago
In the question above
is "A pupil's" mean "A student" ?
is "A pupil's" mean "A student" ?
Sahithi said:
1 decade ago
Short cut method:
Here given avg incresed 1/2 means 0.5
Taken 83 instead of 63 the differnce of avg incresed 83-63=20
Therefore how many 1/2 s in 20 ?
for detailed
1 means 1/2+1/2 contain 2 halfs
20 contain 20*2=40 halfs
Therefore n=40 pupils.
Here given avg incresed 1/2 means 0.5
Taken 83 instead of 63 the differnce of avg incresed 83-63=20
Therefore how many 1/2 s in 20 ?
for detailed
1 means 1/2+1/2 contain 2 halfs
20 contain 20*2=40 halfs
Therefore n=40 pupils.
Yuvraj.. said:
1 decade ago
@priya:
Increase in avg. marks of class * no. of students = increase in marks of a student---->eqn 1
Now; increase in avg marks of class = 1/2= 1.5
and increase in marks of a student = 83-63= 20
therefore
from eqn 1
no. of students = increase in marks of a student/ increase in avg marks of class
So,
No. of students=20/1.5= 40
Increase in avg. marks of class * no. of students = increase in marks of a student---->eqn 1
Now; increase in avg marks of class = 1/2= 1.5
and increase in marks of a student = 83-63= 20
therefore
from eqn 1
no. of students = increase in marks of a student/ increase in avg marks of class
So,
No. of students=20/1.5= 40
Priya said:
1 decade ago
Please trace where I went wrong.
Let n be total number of students
When marks was entered as 63 -----(x+63)/n=1 . . eqn1
When enterd as 83--------(x+83)/n=1.5. . . .eqn2
eqn1 --->n=x+63
eqn2---->n=(x+83)/1.5
equatin both x+63=(x+83)/1.5
1.5x+94.5=x+83
.5x=11.5
x=23
bak sub in eqn1
23+63=n
n=86
Please help me.
Let n be total number of students
When marks was entered as 63 -----(x+63)/n=1 . . eqn1
When enterd as 83--------(x+83)/n=1.5. . . .eqn2
eqn1 --->n=x+63
eqn2---->n=(x+83)/1.5
equatin both x+63=(x+83)/1.5
1.5x+94.5=x+83
.5x=11.5
x=23
bak sub in eqn1
23+63=n
n=86
Please help me.
Ravi said:
1 decade ago
Thanks habib.
M.V.KRISHNA/PALVONCHA said:
1 decade ago
Hai nik. Your explanation is nice.
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