New PMP Question & Answers with explanation

Crashing is an effective schedule compression technique at times when a project is struggling behind schedule. However, increasing the number of resources to twice the original number of the resources does not always cut the time by half. This is due to:
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Andy’s project stakeholders are not happy as the project is lagging behind schedule. During the executive committee meeting, Andy requests all stakeholders to keep their calm as most of the project deliverables have been completed and only quality inspections of these deliverables is pending. He assures the stakeholders that he is planning to crash the project to meet the completion deadline. What should be the stakeholders’ biggest concern now?
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Your construction project is in execution, and you require a major change to one of your supplier agreements. Can you directly make this change with mutual consent of the supplier during the Control Procurements process, or do you have to visit the Perform Integrated Change Control process, as well?
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You have recently taken over a project as the project manager. The project is midway through execution, and most of the project work has been subcontracted. You have just found out that one of the subcontractors, who was responsible for all demolitions, has been paid 50 percent of the subcontracted value, but he has delivered only 25 percent of the required works. Upon investigation, you learned that all the payments are in line with the signed contract between the two parties and the subcontractor’s work is compliant with the contract specifications. You are annoyed because this does not give you enough control over the subcontracted works. Which of the following is not an appropriate thing to do at this stage?
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You have recently joined an organization as the procurements manager. You have just received an invoice from a contractor. Some of the items from the invoice are as follows: EV of work completed to date: $50,000. AC of work completed to date: $40,000. Total costs reimbursed by the buyer to date: $35,000. If the contract between the buyer and the contractor is a CPIF contract, what is the total value payable to this contractor? (Assume that the contract allows for a 10 percent fee over net payable whenever CPI > 1).
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