If |a-b|=c, what is the value of a?
(1) b = 2
(2) c = 7
The OA is the option E.
Why using both statements together is not sufficient? I think that a=9. Am I wrong?
If |a-b|=c ,what is the value of a?
This topic has expert replies
GMAT/MBA Expert
- ErikaPrepScholar
- Legendary Member
- Posts: 503
- Joined: Thu Jul 20, 2017 9:03 am
- Thanked: 86 times
- Followed by:15 members
- GMAT Score:770
If |a-b|=c, then we can have either $$a-b=c\ \ OR\ \ a-b=-c$$ because of the properties of absolute values. For the statements to be sufficient, we need to find only one possible value for a. So unless we get a single value for a with BOTH equations, the statements are insufficient to solve.
You've already worked through why the statements individually aren't sufficient to solve, so we'll look at them together:
If b = 2 and c = 7, we can have either $$a-2=7\ \ OR\ \ a-2=-7$$
Solving for a in both equations gives $$a=9\ \ OR\ \ a=-5$$
This means that there are two possible values for a: 9 and -5. Insufficient.
You've already worked through why the statements individually aren't sufficient to solve, so we'll look at them together:
If b = 2 and c = 7, we can have either $$a-2=7\ \ OR\ \ a-2=-7$$
Solving for a in both equations gives $$a=9\ \ OR\ \ a=-5$$
This means that there are two possible values for a: 9 and -5. Insufficient.
Erika John - Content Manager/Lead Instructor
https://gmat.prepscholar.com/gmat/s/
Get tutoring from me or another PrepScholar GMAT expert: https://gmat.prepscholar.com/gmat/s/tutoring/
Learn about our exclusive savings for BTG members (up to 25% off) and our 5 day free trial
Check out our PrepScholar GMAT YouTube channel, and read our expert guides on the PrepScholar GMAT blog