The correct answer is $680, although many people mistakenly answer $650. Let's break down the problem to understand why.

Step-by-Step Solution

Initial Calculation: $5/page x 100 pages = $500

Revised Pages Calculation: 40 pages x $3/page = $120

Twice Revised Pages Calculation:

• Error: 1 more revision of 10 pages x $3 = $3o
• Correct: 10 pages x $6 = $60

Answer: $680

The 10 pages revised twice were not necessarily part of the 40 pages revised only once therefore require the cost of $3 for each revision.

Key Takeaways

• Attention to Detail: The problem is tricky because it requires careful reading and understanding of each part. Misinterpretation can lead to incorrect answers.
• Common Errors: The typical error is assuming the 10 pages revised twice are part of the 40 pages revised once, which is not stated in the problem.
• Deliberate Reading: Always read and reread the problem to ensure a thorough understanding. Casual reading can lead to mistakes, not due to a lack of math or logic skills, but due to misunderstanding the problem.

By following these steps and being meticulous in reading the problem, you can avoid common pitfalls and arrive at the correct solution.