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OG 12 DS #97

by Niner710 » Fri Nov 20, 2009 7:41 pm
If Aaron, Lee and Tony have a total of $36, how much money does Tony have?
1) Tony has twice as much money as Lee and 1/3 as much as Aaron.
2) The sum of the amounts of money that Tony and Lee have is half the amount that Aaron has.

It seems like an easy question but 1) tripped me up for some reason. Can someone give me a better explanation then OG.
It seems I approached it the wrong way.

For 1)
T = 2L
T = 1/3A
A + L + T = 36

The OG uses part vs. whole but I guess I don't understand why my way of approaching the problem doesn't work.

Can someone explain? Thanks.
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by thephoenix » Fri Nov 20, 2009 7:53 pm
from Q stem we get
A+L+T=36

FROM S1)
T=2L--------->L=T/2
T=1/3A------>A=3T

i.e
3T+T/2+T=36
9T/2=36
T=8

HENCE SUFF.

S2)
A=(L+T)/2------------>L+T=2A
NOT SUFF
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by singalong » Sat Jan 21, 2012 11:29 pm
For statement 2, Isn't it T+L= A/2?
I always end up equating wrong.
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by mj78ind » Sun Jan 22, 2012 8:31 am
thephoenix wrote:from Q stem we get
A+L+T=36

FROM S1)
T=2L--------->L=T/2
T=1/3A------>A=3T

i.e
3T+T/2+T=36
9T/2=36
T=8

HENCE SUFF.

S2)
A=(L+T)/2------------>L+T=2A
NOT SUFF
Just to extend the discussion above. usually one needs 3 equations to solve 3 unknowns, but GMAT can throw a curve ball!
Imagine if the question had said - How much does A have?

Now, stmt 1 and stmt 2 can both answer the question separately! Even though in Stmt 2, there are 2 equations and 3 unknowns! But L and T can be substituted with A thus we can get a value of A from the two equations. See below:

A+L+T = 36 ------- 1
A = (L+T)/2 ------- 2
3A = 36 or A = 12 (substituting for L+T in equation 1 from equation 2)

Hope this gave an added dimension to an already solved question. When I was preparing for the test, I would look at such questions and think to myself how could it be made trickier or tougher (say 500+ question to a 700+ question) and I would come up with these ideas. The good part about such an exercise is that it keeps one agile, you are most probably not going to get the above question in the actual exam. You might get a variant. With this kind of brain storming you have actually created your own variant! Thus, your chances of solving "non-seen" questions increases.

Cheers
Call me 1 - (412) 897 6727 (US) or leave a msg on BTG for GMAT advise / questions.
If you like the solution, check out my debrief at and leave a comment:
https://www.beatthegmat.com/760-done-dea ... 66740.html
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