Aptitude - Percentage - Discussion
Discussion Forum : Percentage - General Questions (Q.No. 9)
9.
| A student multiplied a number by | 3 | instead of | 5 | . |
| 5 | 3 |
What is the percentage error in the calculation?
Answer: Option
Explanation:
Let the number be x.
| Then, error = | 5 | x - | 3 | x = | 16 | x. |
| 3 | 5 | 15 |
| Error% = |  |
16x | x | 3 | x 100 |  % = 64%. |
| 15 | 5x |
Discussion:
134 comments Page 14 of 14.
SATHISHKUMAR R said:
4 years ago
Formula:
%of error = Question/comparison value * 100.
Here the question is finding an error.
Comparison is the true value.
3/5 x-5/3 x = 16/15 (LCM)/x means unknown value.
16/15 /(5/3) *100 = 64%.
%of error = Question/comparison value * 100.
Here the question is finding an error.
Comparison is the true value.
3/5 x-5/3 x = 16/15 (LCM)/x means unknown value.
16/15 /(5/3) *100 = 64%.
Insaan said:
4 years ago
To find error = true value - false value.
So, 5/3 - 3/5 ( to subtract we need to make denominator same) ( here multiply 3*5= 15)
5*5/3*5 - 3*3/5*3 = 25/15 - 9/15,
= 16/15.
To now find error %
Take the 16/15 *3/5 *100( taking 100 bcos its in percentage),
48/75 *100,
64%.
So, 5/3 - 3/5 ( to subtract we need to make denominator same) ( here multiply 3*5= 15)
5*5/3*5 - 3*3/5*3 = 25/15 - 9/15,
= 16/15.
To now find error %
Take the 16/15 *3/5 *100( taking 100 bcos its in percentage),
48/75 *100,
64%.
Pooja said:
4 years ago
@Pradip Zala: at last, why we take 100/500. Can you explain?
Ashi said:
5 days ago
Take LCM of the denominator i.e 3 x 5 = 15.
3/5*15 = 9 (this is the number we mistakely multiplied)
(but the number should have been this all along ) 5/3 * 15 = 25.
Difference -> 25 - 9 = 16.
Now, 16/25(the right number)* 100 = 64%.
3/5*15 = 9 (this is the number we mistakely multiplied)
(but the number should have been this all along ) 5/3 * 15 = 25.
Difference -> 25 - 9 = 16.
Now, 16/25(the right number)* 100 = 64%.
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