I need help with GMAT RC main idea / primary purpose questions.

Those sorts of questions, which require you to understand the "big picture" of a passage, can definitely be tricky! You know you've encountered one when you see one of these phrases in the text of the question: 

• “The author’s primary purpose in this passage is . . .”
• “The passage is mainly concerned with . . .”
• “The best title for this passage would be . . .”
• “The author’s discussion of … is primarily intended to explain . . .”
• “Which of the following most completely and accurately describes the passage . . .”

Kevin discusses how to solve main idea questions in this excellent GMAT Tuesdays video. He recommends a four step strategy to tacking main idea questions. Here are the steps: 

1. Attack the passage. Every time you read a GMAT passage, you should read actively: that means looking the passage's main idea, its structure, and the author's tone. When you get to main idea questions, you will already have thought about the main idea of the passage while you were reading it! :) 
2. Re-phrase the question in your own words. This will help you understand what information you're looking for in the passage, which can making finding the correct answer a lot easier. 
3. Anticipate the answer. Looking at the passage and finding an answer to the question before you look at the answer choices can prevent you from falling prey to "trap answers." 
4. Eliminate wrong answers. This is generally easier than looking for the right answer. Once you've eliminated all the wrong answers, you'll know which one is correct! :D 

Also make sure you watch our lesson video on Primary Purpose questions. 

I hope you find these resources helpful. Happy studying!