GMAT Problem Solving strategy: test answer choices

si working krakenOne way to quickly answer questions when you are stumped is to try to test answer choices.  You are only given five, so sometimes this will get you to the correct answer faster than doing the work to multiply the problem out.

You can rent DVDs at a local video store for 5.00 per movie without a membership.  However, if you purchase a membership for 7.00 per month, you can rent DVDs for 2.00 a piece.  What is the minimum amount of DVDs you would have to rent to make it worth it to purchase the membership.

  • (A) 1
  • (B) 2
  • (C) 3
  • (D) 4
  • (E) 5

Because this question is asking for the minimum amount, you can start testing with the lowest number and work your way up.  Once you find a value where the membership costs less than the non membership, you have found your answer.

(A) with the membership its $9 and without its 5, so this isn’t our answer

(B) with the membership its $11 and without its  $10, so also no

(C) with the membership its $13 and without its $15, so now we have found our answer!

The other way to have done this would have been to create an algebraic equation, set the two sides equal to each other and solve for x, then figure out the next value, like so:

7+2x=5x

7=3x

x=7/3 or 2 1/3

we could then deduce that the right answer is 3, because you can’t rent half a DVD

However, with problems like these it’s often faster to simply check answers and at the end of the day, we want to get though the problems in the quickest way possible.   

Meet the Author

Eliza Chute

I was always just an average student, but with the right course prep I was able to score a 770 on my first try. I had to wade through a lot of material to find what was right for me, but luckily for you I've done all the research for you! See more on my GMAT courses page.

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