What is the value of |x + 5| + |x - 3|?
1. x^2 < 25
2. x^2 > 9
[spoiler]OA: E[/spoiler]
What is the value of |x + 5| + |x - 3|? Exam pack 2
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Hi prata,
This question can be solved by TESTing VALUES.
We're asked for the value of |X + 5| + |X - 3|.
1) X^2 < 25
IF...
X = 4
then the answer to the question is |9| + |1| = 10
IF...
X = 3
then the answer to the question is |8| + |0| = 8
Fact 1 is INSUFFICIENT
2) X^2 > 9
IF...
X = 4
then the answer to the question is |9| + |1| = 10
IF...
X = 5
then the answer to the question is |10| + |2| = 12
Fact 2 is INSUFFICIENT
Combined, we know that....
X^2 < 25
X^2 > 9
At first glance, you might think that X=4 is the only possibility. HOWEVER, we were never told that X had to be an integer (so it could be 3.5 or 4.9999, for example). TESTing any of those possibilities will prove that the answer to the question changes...
IF...
X = 4
then the answer to the question is |9| + |1| = 10
IF...
X = 3.5
then the answer to the question is |8.5| + |.5| = 9
Combined, INSUFFICIENT
Final Answer: E
GMAT assassins aren't born, they're made,
Rich
This question can be solved by TESTing VALUES.
We're asked for the value of |X + 5| + |X - 3|.
1) X^2 < 25
IF...
X = 4
then the answer to the question is |9| + |1| = 10
IF...
X = 3
then the answer to the question is |8| + |0| = 8
Fact 1 is INSUFFICIENT
2) X^2 > 9
IF...
X = 4
then the answer to the question is |9| + |1| = 10
IF...
X = 5
then the answer to the question is |10| + |2| = 12
Fact 2 is INSUFFICIENT
Combined, we know that....
X^2 < 25
X^2 > 9
At first glance, you might think that X=4 is the only possibility. HOWEVER, we were never told that X had to be an integer (so it could be 3.5 or 4.9999, for example). TESTing any of those possibilities will prove that the answer to the question changes...
IF...
X = 4
then the answer to the question is |9| + |1| = 10
IF...
X = 3.5
then the answer to the question is |8.5| + |.5| = 9
Combined, INSUFFICIENT
Final Answer: E
GMAT assassins aren't born, they're made,
Rich
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Hi Rich,[email protected] wrote:Hi prata,
This question can be solved by TESTing VALUES.
We're asked for the value of |X + 5| + |X - 3|.
1) X^2 < 25
IF...
X = 4
then the answer to the question is |9| + |1| = 10
IF...
X = 3
then the answer to the question is |8| + |0| = 8
Fact 1 is INSUFFICIENT
2) X^2 > 9
IF...
X = 4
then the answer to the question is |9| + |1| = 10
IF...
X = 5
then the answer to the question is |10| + |2| = 12
Fact 2 is INSUFFICIENT
Combined, we know that....
X^2 < 25
X^2 > 9
GMAT assassins aren't born, they're made,
Rich
I believe I can use x=4 and x=-4
fact 1)
x=4.........|9| + |1| = 10
x=-4........|1| + |-7| = 8 Insuff
fact 2) I can use same examples above .....Insuff
combining 1 &2 with same examples above in so Insuff
Answer E
Is my examples correct? can I use x=-4???
Thanks
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What is the value of |x + 5| + |x - 3|?prata wrote:What is the value of |x + 5| + |x - 3|?
1. x^2 < 25
2. x^2 > 9
The critical points are the values that make the absolute values equal to 0.
Here, the critical points are -5 and 3.
The distance between the critical points is the LEAST POSSIBLE VALUE for the expression in blue.
The distance between -5 and 3 is 8.
Thus, the least possible value for the expression in blue is 8.
If x is between the critical points of -5 and 3, inclusive, then the expression in blue will be equal to the LEAST POSSIBLE VALUE (8):
If x=0, then |x + 5| + |x - 3| = |0+5| + |0-3| = 8.
If x=-2, then |x + 5| + |x - 3| = |-2+5| + |-2-3| = 8.
If x=3, then |x + 5| + |x - 3| = |3+5| + |3-3| = 8.
If x is NOT between the critical points of -5 and 3, inclusive, then the expression in blue will be equal to a VALUE GREATER THAN 8:
If x=4, then |x + 5| + |x - 3| = |4+5| + |4-3| = 10.
If x=10, then |x + 5| + |x - 3| = |10+5| + |10-3| = 22.
If x=-7, then |x + 5| + |x - 3| = |-7+5| + |-7-3| = 12.
Both statements are satisfied by x=-4.
In this case, x is between -5 and 3, inclusive, so the expression in blue will be equal to the least possible value (8).
Both statements are satisfied by x=4.
In this case, x is NOT between -5 and 3, inclusive, so expression in blue will equal to a value greater than 8.
Since the expression in blue can be different values, the two statements combined are INSUFFICIENT.
The correct answer is E.
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I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
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Hi Mo2men,
Yes - very good!; you can absolutely use negative values when TESTing VALUES in this prompt. One of my default 'rules' for dealing with DS questions is that if there's an inconsistent result to be found (in this case, the answer to the 'value' question changes), then I have to find it (and that might involve TESTing negatives, 0, fractions, etc.).
GMAT assassins aren't born, they're made,
Rich
Yes - very good!; you can absolutely use negative values when TESTing VALUES in this prompt. One of my default 'rules' for dealing with DS questions is that if there's an inconsistent result to be found (in this case, the answer to the 'value' question changes), then I have to find it (and that might involve TESTing negatives, 0, fractions, etc.).
GMAT assassins aren't born, they're made,
Rich