VICs - when to plug in a variable? when to solve?

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Is there a guidline or strategy for this, or is it just "learn by doing?"

For example, I had a VIC question which I tried to solve, but the answer said it was easier to plug a number in. I get it.

Then, I had an OG12 problem (somewhere in the 160s or 170s) that went something like this.

Bob saves some money and spends some. How much does he have to save this year if it grows at (1+r) if he wants have as much as he spends next year and if he has no income next year.

So you start with:
(s)(1+r) = (I-s)/2

where I = income and s = savings.

Now, intuitively, I would try to plug in numbers - I wouldn't think to solve for (I-s). The book solves for I and substitutes it into s/I, which makes sense. I recognize the book doesn't always have the best strategies and I'm sure plugging in number would work, but I would get confused in terms of extracting the answer.

So...any guidlines?
Last edited by salmaan on Tue Mar 16, 2010 8:39 am, edited 1 time in total.
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by Osirus@VeritasPrep » Tue Mar 16, 2010 5:43 am
There is no "right" answer to this. I would recommend learning both. If you only know how to plug in without fully understanding the underlying algebra, on test day, you may find plugging in more difficult on some of the more difficult problems. This was my experience anyway. The test makers are really good at what they do, they know the strategies that test prep companies teach, so once you start hitting above a certain level, the questions are going to be designed to seperate those that are only good at certain strategies from those that have an in depth knowledge of the material. Good luck.
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