Math Is Fun Forum

DragonflyVerite

Member

Registered: 2007-09-11

Posts: 1

Gre Math

Hi Everyone,
    I am in desperate need of GRE math help...I am already enrolled in a Kaplan prep course, but homework in between sessions and studying on my own is challenging.  I find the hardest thing for me to do is know how to set up an equation for a specific problem.  For example...here is one of the questions:

A vending machine sells 35 snacks for a total of 17.00.  Some snacks are sold for 40 cents and the rest are sold for 55 cents.  How many snacks were sold for 55 cents?  (For this problem we were taught to use the backsolving method where you plug in the answer choices into the formula you create - and I have no problem with that, but it's setting up the actual equation!!!)

Can anyone give me tips on how to approach setting up equations without panicking?  I just look at those questions and completely freak!!!

Thanks so much!!!

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Gre Math

Because I can't think of anything more appropriate, represent the number of cheap snacks sold by A and the number of expensive snacks by B.

The first sentence says that 35 snacks are sold, so you can get A+B = 35 from that.
Then you're told that it collects 17.00, which means that 0.4A + 0.55B = 17.

You now have two equations with two variables and so you can solve it.
I'm not familiar with the backsolving method, but if that's not the bit you're struggling with then it's not a problem.

So you can check, your answer should be

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Why did the vector cross the road?
It wanted to be normal.

DragonflyVerite

Member

Registered: 2007-09-11

Posts: 1

Re: Gre Math

Thank you so much!!!