|
|
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
29 May 2023, 07:30
Kudos
Bookmarks
E
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
65%
(hard)
Question Stats:
60% (02:09) correct
40%
(02:47)
wrong
based on 173
sessions
History
Date
Time
Result
Not Attempted Yet
\(x^3-y^3 = 90\) and \(x-y = 3\). What is the value of \(xy\)?
A. 3
B. 4
C. 5
D. 6
E. 7
A. 3
B. 4
C. 5
D. 6
E. 7
31 May 2023, 06:24
Kudos
Bookmarks
Bunuel
We can use the standard identity
\((x - y)^3 = x^3 - y^3 -3xy(x-y) \)
\((3)^3 = 90 -3xy(3) \)
\(9xy = 90 - 27\)
\(xy = 10 - 3 = 7\)
Option E
01 Jun 2025, 05:15
Kudos
Bookmarks
\(x^3-y^3 = 90\) and \(x-y = 3\).
What is the value of \(xy\)?
\(x^3 - y^3 = 90 = (x-y)(x^2 + y^2 + xy) = 3(x^2 + y^2 + xy) = 3( (x-y)^2 + 3xy ) = 3(9 + 3xy)\)
27 + 9xy = 90
\(xy = \frac{(90-27)}{9} = 7\)
IMO E
What is the value of \(xy\)?
\(x^3 - y^3 = 90 = (x-y)(x^2 + y^2 + xy) = 3(x^2 + y^2 + xy) = 3( (x-y)^2 + 3xy ) = 3(9 + 3xy)\)
27 + 9xy = 90
\(xy = \frac{(90-27)}{9} = 7\)
IMO E
