Workers leave partway through a men-days job

This type of question, asked 2 times: CDS 2 2017, CDS 1 2024. All 2 questions below, oldest first.

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Question 1
CDS 2 2017
37 $30 men can complete a job in 40 days. However, after 24 days some men out of the assigned 30 left the job. The remaining people took another 40 days to complete the job. The number of men who left the job is$
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Question 2
CDS 1 2024
29 $50 men can complete a work in 40 days. They begin the work together but a batch of 5 men left after each period of 10 days. What is the time to complete the work ?$
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Question 1