If |a - b| = 6 and |b - c| = 15, then what is the value of |c|?
(1) |a - c| = 9
(2) |b| = 9
Source: Empowergmat
Solution
Fact 2) |b| = 9 ..........it means that b=9 or b=-9
When b= 9
|9 - c| = 15 ............ C= -6 or C= 24
|-9 - c| = 15 ............ C= 6 or C= -24
Insufficient
Fact 1) |a - c| = 9
As both facts do not contradict each other, we can use the info of fact 1
When b=9 & From |a - b| = 6...............a = -3 or 15
When c=24 & Using fact 1.... |a - c| = 9 .........a = 33 or 15
Then a =15
When b=-9, c=6
When b=-9 & From |a - b| = 6...............a = -3 or -15
When c=6 & Using fact 1.... |a - c| = 9 .........a = -3 or 15
Then a =-3
We have two sets that stratifies 3 equations
Insufficient
Combined 1 & 2, No certain answer reached
Answer: E
Is my solution valid? Is there any easier solution
Thanks
high Level Absolute question
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|x-y| = the DISTANCE between x and y.Mo2men wrote:If |a - b| = 6 and |b - c| = 15, then what is the value of |c|?
(1) |a - c| = 9
(2) |b| = 9
According to the prompt:
The distance between a and b is 6.
The distance between b and c is 15.
According to Statement 1:
The distance between a and c is 9.
Statement 2:
Let b=9.
Since this problem involves multiple DISTANCES, plot options on a NUMBER LINE:
Case 1:
c=-6 and a=3 satisfy the constraints that |a - b| = 6 and |b - c| = 15.
These values also satisfy Statement 1, since |a - c| = 9.
In this case, |c| = 6.
Case 2:
a=15 and and c=24 satisfy the constraints that |a - b| = 6 and |b - c| = 15.
These values also satisfy Statement 1, since |a - c| = 9.
In this case, |c| = 24.
Since Cases 1 and 2 satisfy both statements but yield different values for |c|, the two statements combined are INSUFFICIENT.
The correct answer is E.
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Followed here and elsewhere by over 1900 test-takers.
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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