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 2 of 6.
Stephen said:
6 years ago
If the fraction is 4/5.
Then 4/5(fraction)-5/4(reciprocal) = -9/20.
So, I believed the answer(fraction) = 5/4.
Then 4/5(fraction)-5/4(reciprocal) = -9/20.
So, I believed the answer(fraction) = 5/4.
Jyothi said:
6 years ago
Thank You @Akash.
Krishna Sowjanya said:
6 years ago
Let the proper fraction be x/y.
Then (x/y)-(y/x) = 9/20.
LCM of x and y = xy.
Therefore the denominator xy =20 obviously.
So, by cross-checking the options in option C we have 4 * 5=20. i.e., x=4 and y=5.
Then (x/y)-(y/x) = 9/20.
LCM of x and y = xy.
Therefore the denominator xy =20 obviously.
So, by cross-checking the options in option C we have 4 * 5=20. i.e., x=4 and y=5.
(1)
Sakshi sharma said:
6 years ago
Why have we taken the fraction as 1/x? what if we take it as a/b?
Puja said:
6 years ago
Can anyone please explain how 25 and 9 came?
Tobzs said:
6 years ago
4+5=9
4 * 5 = 20,
And 9/20 = 4/5 in the simplified form
So, 4/5 is the answer.
4 * 5 = 20,
And 9/20 = 4/5 in the simplified form
So, 4/5 is the answer.
Anomi said:
7 years ago
It must be x-1/x=9/20 in the first place.
Since +ve proper fraction x is always greater than it's reciprocal. For eg if we consider 3 as +ve proper fraction, then it's reciprocal is 1/3 which is obviously lesser than 3.
Since +ve proper fraction x is always greater than it's reciprocal. For eg if we consider 3 as +ve proper fraction, then it's reciprocal is 1/3 which is obviously lesser than 3.
Suresh said:
7 years ago
What is factorization? I am not understanding this.
Vicky said:
7 years ago
I think the right answer is 5/4.
Ref: RS Agarwal.
Ref: RS Agarwal.
(1)
Dharna said:
7 years ago
Answer should be 5/4 not 4/5.
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