What is the value of xy?
(1) y = x + 1
(2) y = x^2 + 1
OA E
Source: Official Guide
What is the value of xy?
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Question: What is the value of xy?
To answer this question, we need either values for x and y individually, or simply a value for the product xy.
(1) y = x + 1
This gives us y in terms of x, but cannot give us the value of xy. Insufficient.
(2) y = x^2 + 1
This gives us y in terms of x^2, but cannot give us the value of xy. Insufficient.
(1) and (2) together
We know the rule that we need 2 equations to solve for the values of 2 variables... but be careful! Even exponents can give us multiple possible values. Let's see what happens when we try to solve:
y = x + 1
y = x^2 + 1
x + 1 = x^2 + 1
x = x^2
x = either 1 or 0
Thus, y = either 2 or 1
Since we have 2 possible sets of values that would give us different values for xy, this is insufficient to answer the question.
The answer is E.
To answer this question, we need either values for x and y individually, or simply a value for the product xy.
(1) y = x + 1
This gives us y in terms of x, but cannot give us the value of xy. Insufficient.
(2) y = x^2 + 1
This gives us y in terms of x^2, but cannot give us the value of xy. Insufficient.
(1) and (2) together
We know the rule that we need 2 equations to solve for the values of 2 variables... but be careful! Even exponents can give us multiple possible values. Let's see what happens when we try to solve:
y = x + 1
y = x^2 + 1
x + 1 = x^2 + 1
x = x^2
x = either 1 or 0
Thus, y = either 2 or 1
Since we have 2 possible sets of values that would give us different values for xy, this is insufficient to answer the question.
The answer is E.
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
GMAT/MBA Expert
- ceilidh.erickson
- GMAT Instructor
- Posts: 2095
- Joined: Tue Dec 04, 2012 3:22 pm
- Thanked: 1443 times
- Followed by:247 members
Timer
00:00
Your Answer
A
B
C
D
E
Global Stats
For more on how the GMAT subverts our expectations of the 2 equations / 2 variables rule, see:
https://www.manhattanprep.com/gmat/blog ... ons-rules/
https://www.manhattanprep.com/gmat/blog ... ons-rules/
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
EdM in Mind, Brain, and Education
Harvard Graduate School of Education