If the difference and product of two numbers are 5 and 36, respectively, what…
2019
If the difference and product of two numbers are 5 and 36, respectively, what is the difference between their reciprocals?
- A.
5/36
- B.
5/9
- C.
31/36
- D.
9/5
Attempted by 3 students.
Show answer & explanation
Correct answer: A
Concept
For two nonzero numbers x and y, subtracting their reciprocals requires a common denominator: 1/y - 1/x = (x - y)/(xy).
Thus, when the difference x - y and the product xy are known, the reciprocal difference can be obtained directly from their ratio.
Application
Let the two numbers be x and y, with x - y = 5 and xy = 36.
Write the reciprocal difference as 1/y - 1/x = (x - y)/(xy).
Substitute the given values: (x - y)/(xy) = 5/36.
Therefore, the difference between the reciprocals is 5/36.
Cross-check
A factor pair satisfying the conditions is x = 9 and y = 4. Then 1/4 - 1/9 = (9 - 4)/36 = 5/36, confirming the result.