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Tricky Systems of Equations (3) Problem

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by EMAN » Thu Nov 12, 2009 8:00 pm
Andrew will be half as old as Larry in 3 years. Andrew will also be one-third as old as Jerome in 5 years. If Jerome is 15 years older than Larry, how old is Andrew?

Please show work and strategy. I got a little confused manipulating the three equations and the explanation is the Manhattan guide is overly tedious in my opinion.
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by gmatv09 » Thu Nov 12, 2009 8:11 pm
A+3 = 1/2 (L+3) ==> 2A+6 = 3 + L

A+5 = 1/3 (J+5) ==> 3A+15 = 20 +L

================
A + 9 = 17
A = 8
J = 15+L
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Great

by EMAN » Thu Nov 12, 2009 8:22 pm
That's good. It looks like I had a few minor errors in my equation setup. Where is 20 + L coming from?
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by EMAN » Thu Nov 12, 2009 8:28 pm
I would think that 3A + 15 = J + 15 (as opposed to L + 20) which I understand would make the equation work.
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Re: Tricky Systems of Equations (3) Problem

by palvarez » Thu Nov 12, 2009 11:53 pm
EMAN wrote:Andrew will be half as old as Larry in 3 years. Andrew will also be one-third as old as Jerome in 5 years. If Jerome is 15 years older than Larry, how old is Andrew?

Please show work and strategy. I got a little confused manipulating the three equations and the explanation is the Manhattan guide is overly tedious in my opinion.
Create a grid or matrix like table, with rows for L, A, J, and with colums for today, today +3, today + 5. Just put all variables. Then come up with equations: this way, you wont get lost in a maze of variables, etc.
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