New PMP Question & Answers with explanation

In projects with adaptive life cycles, the overall scope of the project will be decomposed into a set of requirements and work to be performed, sometime referred to as:
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What is the MAIN reason for controlling the project scope?
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The sponsor of your facilities upgrade project has left the company to join another organization. Several weeks later, you are reviewing the business case for the project, and you find that there are several inconsistencies between what is stated in the business case and what is described in the project scope. Further research shows that the business case as a whole is based on inaccurate information. What do you do?
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A project is contracted on a Cost-Plus-Fixed-Fee (CPFF) basis with a fee of 10 percent of estimated costs. The estimated cost is US$50,000. If the project comes in at US$75,000 with no changes in project scope, what would be the total cost of the contract?
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A first-time project manager wanted to have a “perfect project.” This manager informed the customer that this project would not accept change requests of any kind and that the scope would need to be defined precisely at the very start of the project. The customer agreed to this request. What would your comment on this situation be?
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