Aptitude - Area - Discussion
Discussion Forum : Area - General Questions (Q.No. 2)
2.
An error 2% in excess is made while measuring the side of a square. The percentage of error in the calculated area of the square is:
Answer: Option
Explanation:
100 cm is read as 102 cm.
A1 = (100 x 100) cm2 and A2 (102 x 102) cm2.
(A2 - A1) = [(102)2 - (100)2]
= (102 + 100) x (102 - 100)
= 404 cm2.
| Percentage error = |
 |
404 | x 100 |  % |
= 4.04% |
| 100 x 100 |
Discussion:
40 comments Page 2 of 4.
Arpita said:
8 years ago
But it isn't given that error is made and the length is increased by 2cm.
I mean 2%of 100 = 2.
But then we can even subtract 2 from 100 which us 98 instead of adding that 2.
Please help me.
I mean 2%of 100 = 2.
But then we can even subtract 2 from 100 which us 98 instead of adding that 2.
Please help me.
Harsh said:
10 years ago
Why is this method wrong?
A = a^2;
dA = 2*a*da;
dA/A = 2*(da/a).
We know da/a = 2%. Hence, dA/A = 4%.
I don't seem to understand the reason why this is wrong? Can someone explain?
A = a^2;
dA = 2*a*da;
dA/A = 2*(da/a).
We know da/a = 2%. Hence, dA/A = 4%.
I don't seem to understand the reason why this is wrong? Can someone explain?
(1)
Kasinath @Hyd said:
1 decade ago
Correct value is 100*100.
Measured value is 102*102.
Therefore ERROR Value is (102*102)-(100*100) = 404.
Error% = (error value/ true value)*100.
=> (404/100*100)*100 = 4.04.
Measured value is 102*102.
Therefore ERROR Value is (102*102)-(100*100) = 404.
Error% = (error value/ true value)*100.
=> (404/100*100)*100 = 4.04.
Jobin said:
7 years ago
Percentage error=
( Experimental value - theoretical value )/theoretical value *100.
Therefore,
Here percentage error= [(102)^2 - (100)^2]/(100)^2,
= 404*100/(100)^2.
( Experimental value - theoretical value )/theoretical value *100.
Therefore,
Here percentage error= [(102)^2 - (100)^2]/(100)^2,
= 404*100/(100)^2.
(1)
Akil said:
3 years ago
It is simple;
Error is 2% so, take it 1.02.
Now one side of a square is 'a'.
Area = (a*1.02)*(a*1.02),
= (a*a*1.0404).
So, the total error in area = 4.04%.
Error is 2% so, take it 1.02.
Now one side of a square is 'a'.
Area = (a*1.02)*(a*1.02),
= (a*a*1.0404).
So, the total error in area = 4.04%.
(3)
Akash Mane said:
2 years ago
Suppose side = 10, Error excess = 2%.
i.e. 10 + 2% = 10.2,
A 1 = 10 * 10 = 100,
A2 = 10.2 *10.2 = 104.4,
A2 - A1 = 104.4 - 100 = 4.04%.
i.e. 10 + 2% = 10.2,
A 1 = 10 * 10 = 100,
A2 = 10.2 *10.2 = 104.4,
A2 - A1 = 104.4 - 100 = 4.04%.
(18)
Pradyumna said:
1 decade ago
@Sikha.
That is (404*100) /(100*100).
Because we are finding the %error.
Where 404 is change in area and (100*100) for original area.
That is (404*100) /(100*100).
Because we are finding the %error.
Where 404 is change in area and (100*100) for original area.
User said:
1 decade ago
@Sreekanth you are right. Thanks for sharing with us. And this seems to be very easy method for solving these kind of problem.
Abhishek Maurya said:
10 years ago
Percentage error = X+Y+(XY)/100.
So, => 2+2+(2*2)/100.
= 4.04.
Note : This method valid for only two values.
So, => 2+2+(2*2)/100.
= 4.04.
Note : This method valid for only two values.
Danah Bader said:
9 years ago
Exactly @Harsh.
The method is wrong!
I don't seem to understand the reason why this is wrong?
The method is wrong!
I don't seem to understand the reason why this is wrong?
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers