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 3 of 4.
Mahesh said:
1 decade ago
Why you all are consider side of the square is 100.
If we are tack original side of the square is 50.
2% error so side is 50*2/100 = 1. So side of square is 51.
= (51)^2 - (50)^2 = (51+50) (51-50) = 101/100 = 1.01 answer.
Please explain me.
If we are tack original side of the square is 50.
2% error so side is 50*2/100 = 1. So side of square is 51.
= (51)^2 - (50)^2 = (51+50) (51-50) = 101/100 = 1.01 answer.
Please explain me.
Srikanth said:
1 decade ago
Remember this formula x+y+(xy/100).
For rectangle x and y are different, I mean length and breadth are different. Here is square so, only single element we can consider x and y as side of the square.
So (+ for increase and "-" for decrease) 2+2+(2*2/100) = 404/100 = 4.04%.
Lets check an example for rectangle if length increased 5% and breadth decreased 4% so the result is
5-4+(5*(-4))/100 = 0.8% over all decrease.
For rectangle x and y are different, I mean length and breadth are different. Here is square so, only single element we can consider x and y as side of the square.
So (+ for increase and "-" for decrease) 2+2+(2*2/100) = 404/100 = 4.04%.
Lets check an example for rectangle if length increased 5% and breadth decreased 4% so the result is
5-4+(5*(-4))/100 = 0.8% over all decrease.
Sakshi said:
1 decade ago
We can also get the percentage by this.
Percentage error = 404/100 = 4.04
Percentage error = 404/100 = 4.04
Anbu said:
1 decade ago
(A2 - A1) = [(102)2 - (100)2] How it come?
Please advise
Please advise
Amrita said:
1 decade ago
To find out error we got to subtract it first.
Shreya singh said:
1 decade ago
In this type of % some usefull idea is to take default no as 100 and in question 2% is error. Hence our no is 100 error no is 102.
So solve further with square formula:
Area= (side)* (side)
So solve further with square formula:
Area= (side)* (side)
Mazher said:
1 decade ago
Why we are taking this three 100's ?
Meghna said:
1 decade ago
@anbu.
Take the formula a^2-b^2
which is equal to (a+b)(a-b) ... so (102-100)(102+100)
Take the formula a^2-b^2
which is equal to (a+b)(a-b) ... so (102-100)(102+100)
Shikha said:
1 decade ago
Why are we dividing 401 by 100 two times and not one time?
Why it is not- (401*100) /100?
Why it is not- (401*100) /100?
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.
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