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Today Jim is twice as old as Fred, and Sam is 2 years younger than Fred. Four years ago Jim was 4 times as old as Sam. How old is Jim now?

8 12 16 20 24

Today Jim is twice as old as Fred --> J=2F; Today Sam is 2 years younger than Fred --> S+2=F; Four years ago Jim was 4 times as old as Sam --> J-4=4*(S-4);

Substitute F: J=2(S+2) and J-4=4*(S-4) --> J=2S+4 and J=4S-12 --> subtract one from another 0=2S-16 --> S=8 --> J=2(S+2)=20.

----------------------------------------------(2x)--------(x)---------(x-2) [let's consider today age of Fred is x, the ages of Jim is 2x, and age of Sam is (x-2)] ------(2x-4)-----(x-4)-------(x-2-4)---------------------------------------[this are the ages of J, F and S 4 years ago]

As, per condition given in the question, ->2x-4= 4(x-6) -> 2x-4=4x-24 -> 20=2x -> x=10

Therefore, 2x=20, this is the age of Jim today. So, the answer is D
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My mantra for cracking GMAT: Everyone has inborn talent, however those who complement it with hard work we call them 'talented'.

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----------------------------------------------(2x)--------(x)---------(x-2) [let's consider today age of Fred is x, the ages of Jim is 2x, and age of Sam is (x-2)] ------(2x-4)-----(x-4)-------(x-2-4)---------------------------------------[this are the ages of J, F and S 4 years ago]

As, per condition given in the question, ->2x-4= 4(x-6) -> 2x-4=4x-24 -> 20=2x -> x=10

Therefore, 2x=20, this is the age of Jim today. So, the answer is D

is pretty nice your method, it depends what is more comnfortable for you.

For me is much faster in this scenario the algebric approach
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Re: Today Jim is twice as old as Fred, and Sam is 2 years younge [#permalink]

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04 Dec 2015, 10:58

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This question can be solved by TESTing THE ANSWERS and doing a bit of arithmetic:

We're asked how old Jim is NOW. We're given three facts to work with: 1) Today, Jim is TWICE as old as Fred 2) Today, Sam is 2 years younger than Fred 3) Four years ago, Jim was 4 times as old as Sam.

Let's TEST Answer B: 12

IF....Jim is currently 12 years old.... Fred is 6 years old Sam is 4 years old 4 years ago, Jim was 8 and Sam was 0, so Jim was NOT 4 times as old as Sam. We need Sam to be OLDER, so everyone else has to be older too. Eliminate Answers A and B.

Next, let's TEST Answer D: 20

IF....Jim is currently 20 years old.... Fred is 10 years old Sam is 8 years old 4 years ago, Jim was 16 and Sam was 4, so Jim WAS 4 times Sam's age. This is an exact MATCH for what we were told, so this MUST be the answer.

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