Workers with given efficiency ratios: one worker's time

This type of question, asked 2 times: CDS 2 2018, CDS 1 2023. All 2 questions below, oldest first.

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Question 1
CDS 2 2018
32 $'A' is thrice as good a workman as 'B' and takes 10 days less to do a piece of work than 'B' takes. The number of days taken by 'B' alone to finish the work is$
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Question 2
CDS 1 2023
8 $A can do a certain work at twice the speed of B. Further, B can do the same work at 1.5 times the speed of C. All of them together can finish the work in 12 days. In how many days can C alone finish the work?$
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Question 1