Lesson: Tips for the Input-Output Approach

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Great tips

Hi! If you were to solve this algebraically, how would you do it? I get to (1 + y/100 + x/100 + xy/100^2) - 1 and that's basically the right answer... but how do you simplify that to match the answer format? I mean, once I know the answer (100+y)(100+x) then multiplying gives me the above expression inside parenthesis.. but if I didn't know that factorization was there, how do you reach to it?
gmat-admin's picture

You're referring to the question that appear at 6:23 in the above video.

You have: (1 + y/100 + x/100 + xy/100²) - 1

Rewrite first part with denominator 100²
We get: (100²/100² + 100y/100² + 100x/100² + xy/100²) - 1
Combine the first 4 terms: (100² + 100y + 100x + xy)/100² - 1
Factor top part to get: (100 + x)(100 + y)/100² - 1

Hmmm, I have a feeling your first expression, (1 + y/100 + x/100 + xy/100²) - 1, is incorrect.

Can you tell me how you got to (1 + y/100 + x/100 + xy/100²) - 1?


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