Aptitude - Numbers - Discussion
Discussion Forum : Numbers - General Questions (Q.No. 26)
26.
The difference between a positive proper fraction and its reciprocal is 9/20. The fraction is:
Answer: Option
Explanation:
| Let the required fraction be x. Then | 1 | - x = | 9 |
| x | 20 |
 |
1 - x2 | = | 9 |
| x | 20 |
20 - 20x2 = 9x
20x2 + 9x - 20 = 0
20x2 + 25x - 16x - 20 = 0
5x(4x + 5) - 4(4x + 5) = 0
(4x + 5)(5x - 4) = 0
| x = | 4 |
| 5 |
Discussion:
53 comments Page 6 of 6.
Eternal said:
4 years ago
It's easy to try all the options in the given condition that is 1/x-x = 9/20.
Here, put x=4/5 in the above equation we get 9/20 so the answer is 4/5.
Hope you get it.
Here, put x=4/5 in the above equation we get 9/20 so the answer is 4/5.
Hope you get it.
(9)
Kazibwe Moses said:
3 years ago
4/5 is wrong it will give us a negative answer.
If we are to prove it;
4/5-its reciprocal,
4/5-5/4 = ((16/25)/20) = -9/20.
If we are to prove it;
4/5-its reciprocal,
4/5-5/4 = ((16/25)/20) = -9/20.
(15)
Pratyush Sharma said:
2 years ago
In the given case, 9/20 is the difference between the fraction and its reciprocal.
We know that the Denominator is always LCM of denominators of the fractions.
So, checking the possibility for 20: 1*20, 2*10, 4*5.
Since 1/20 and 2/10 are not possible because it is given that the first fraction is proper 20 - 1/20 will never yield 9/20.
So, the answer will be 4/5.
We know that the Denominator is always LCM of denominators of the fractions.
So, checking the possibility for 20: 1*20, 2*10, 4*5.
Since 1/20 and 2/10 are not possible because it is given that the first fraction is proper 20 - 1/20 will never yield 9/20.
So, the answer will be 4/5.
(4)
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