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 12 of 13.
Ajay said:
1 decade ago
Ans of Savinder question
Let total no of cand-x
Dec in aver- 50-45=5
Total dec in numbers= 5x
then, 5x= 100(90-60)
x=600 ( Ans)
Let total no of cand-x
Dec in aver- 50-45=5
Total dec in numbers= 5x
then, 5x= 100(90-60)
x=600 ( Ans)
(1)
Nehanshu raj badholiya said:
1 decade ago
Rakesh's and habi bbhaijan both are correct so don't get confused.
Savinder said:
1 decade ago
In an exam, the average was found to be 50 marks. After detecting computer errors, the marks of 100 candidates had to be changed from 90 to 60 each and the average came down to 45. The total number of candidates who took the exam was:.
Please solve.
Please solve.
Habib said:
1 decade ago
Frnz....dnt get confused boy that 1/2 factor !!!!
see,
(total marks)/(no. of pupils)= avg
OR
total marks = avg X no. of pupils
Given, increase is of 1/2 , no. of pupils=x
total marks increased : 83-63 = 20
Hence, for 1/2 mark avg increase, we use
20 = (1/2) * x OR x=40
see,
(total marks)/(no. of pupils)= avg
OR
total marks = avg X no. of pupils
Given, increase is of 1/2 , no. of pupils=x
total marks increased : 83-63 = 20
Hence, for 1/2 mark avg increase, we use
20 = (1/2) * x OR x=40
Sachin Bende said:
1 decade ago
@ swathy
rakesh's logic is absolutely correct..
explanation:
=(avg mark+1/2)*x - (avg mark*x)
taking "x" common we get,
=x(avg mark + 1/2 - avg mark)
cancelling avg mark
hence,we get
= x(1/2)= 1/2*x
therefore,
83-63=1/2*x
x=20*2=40
ok got it.
rakesh's logic is absolutely correct..
explanation:
=(avg mark+1/2)*x - (avg mark*x)
taking "x" common we get,
=x(avg mark + 1/2 - avg mark)
cancelling avg mark
hence,we get
= x(1/2)= 1/2*x
therefore,
83-63=1/2*x
x=20*2=40
ok got it.
Nik said:
1 decade ago
Avg = sum of marks of each studnt/total no of studnts
= s/n
according to the given condition
(s+20)/n = (s/n)+0.5 ....(here 1/2 is considered as 0.5)
cross multiplying we get,
s+20 = s + 0.5n
so, n = 40
= s/n
according to the given condition
(s+20)/n = (s/n)+0.5 ....(here 1/2 is considered as 0.5)
cross multiplying we get,
s+20 = s + 0.5n
so, n = 40
Swathy said:
1 decade ago
Rakesh I cant understand your logic can you explain clearly?.
Rakesh said:
1 decade ago
If mark=63,then total mark(mark1+mark2+---+63) =(average mark*x)-(1)
but in the qst given that enterd mark is 83 instead of 63,then avg is increased by 1/2(half),
then total mark(mark1+mark2+----+83)=(avg mark+1/2)*x -(2)
eq(2)-eq(1)
83-63=1/2*x;
x=20*2=40
but in the qst given that enterd mark is 83 instead of 63,then avg is increased by 1/2(half),
then total mark(mark1+mark2+----+83)=(avg mark+1/2)*x -(2)
eq(2)-eq(1)
83-63=1/2*x;
x=20*2=40
Krishna kanth said:
1 decade ago
I didn't understand anything please please please some body explain.
Arunoid said:
1 decade ago
Please help the needy and me too.
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