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.
Sai said:
9 years ago
The Best Way Is:
x/y - y/x = 9/20 (Given) -------------(1)
verify with options: I have done with option 4,.
Here x = 4,y = 5;
Substitute in (1)
4/5 - 5/4 = 9/20.
Then, l.h.s = r.h.s.
x/y - y/x = 9/20 (Given) -------------(1)
verify with options: I have done with option 4,.
Here x = 4,y = 5;
Substitute in (1)
4/5 - 5/4 = 9/20.
Then, l.h.s = r.h.s.
(1)
Akhilkondaparva said:
9 years ago
x = 4/5.
=> (1/x) - x = (5/4) - (4/5),
= (25-16) /20 =9/20 (+Positive).
=> x - (1/x) = (4/5) - (5/4),
= (16-25) /20 = -9/20 (-Negative).
I hope you will get this.
=> (1/x) - x = (5/4) - (4/5),
= (25-16) /20 =9/20 (+Positive).
=> x - (1/x) = (4/5) - (5/4),
= (16-25) /20 = -9/20 (-Negative).
I hope you will get this.
(1)
Vicky said:
7 years ago
I think the right answer is 5/4.
Ref: RS Agarwal.
Ref: RS Agarwal.
(1)
Akshat said:
8 years ago
The conventional approach will be the lengthy one for this question.
So by checking all the options we get the option (d),
i.e 5/4-4/5 = 9/20.
So by checking all the options we get the option (d),
i.e 5/4-4/5 = 9/20.
Saurin said:
8 years ago
Thank you all.
Samyuktha said:
8 years ago
If the ans is 4/5.
4/5 - 5/4 should be 9/20 which is not right.. 4/5 - 5/4 is - 9/20.
The answer should be 5/4.
4/5 - 5/4 should be 9/20 which is not right.. 4/5 - 5/4 is - 9/20.
The answer should be 5/4.
Vijay said:
8 years ago
They told in question the difference between +ve proper fraction and its reciprocal is 9/20. Means -> Positive proper fraction=1/x and its reciprocal is 1/1/x=x. Their difference is (1/x) -x=9/20. So we have to find x. Find x by the above method.
Pooja said:
8 years ago
@ Rima.
The numerator is less than the denominator.
Examples: 1/3, 3/4, 2/7. Improper Fractions: The numerator is greater than (or equal to) the denominator.
The numerator is less than the denominator.
Examples: 1/3, 3/4, 2/7. Improper Fractions: The numerator is greater than (or equal to) the denominator.
Shiva said:
8 years ago
Positive proper function is in form of 1/x and its reciprocal is x that why we are considering 1/x - x = 9/20.
Dharna said:
7 years ago
Answer should be 5/4 not 4/5.
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