Hi boomgoesthegmat,
You've been posting large blocks of questions, but you haven't discussed any of YOUR attempt at solving them. Why did you get them wrong? What did you miss? What aspect of each question are you really interested in. It's a good bed that all of these questions have been discussed somewhere online already, so what specifically are you looking for when YOU post them?
This question can be solved by TESTing THE ANSWERS. From the prompt, we know that we're going to be doing a number of small calculations AND we're going to end with 720 acres remaining for corn. Since we're asked for the total number of acres, and the answers are all numbers, we just have to work until we find the one that matches what we've been told. In these situations, it's often best to start with Answer B or D. Between those 2 options, D looks 'nicer'/easier, so let's start there.
IF....there were 8000 total acres...
90% was cleared for planting = (.9)(8000) = 7200 acres for planting
Of that land,
40% was soybeans = (4.)(7200) = 2880 acres
50% was wheat = (.5)(7200) = 3600
2880 + 3600 = 6480
7200 - 6480 = 720 --> this is an exact match for what we were told, so this MUST be the answer.
Final Answer: D
GMAT assassins aren't born, they're made,
Rich
