A works every day, assisted by B and C every nth day: time to finish

The same question, asked 4 times: 26 Jul 2023 S3*, 27 Jul 2023 S2*, 12 Sep 2025 S2*, 16 Sep 2025 S2. Every wording below, oldest first.

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Question 1
26 Jul 2023 S3
65 $X , Y and Z can complete a work in 5 days, 15 days and 30 days, respectively. In how days can the work be completed if X is assisted by Y and Z together, on every second day?$
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Question 2
27 Jul 2023 S2
63 $A, B and C can do a piece of work in 20, 30 and 60 days, respectively. In how many days can A do the work if he is assisted by both B and C on every third day?$
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Question 3
12 Sep 2025 S2
62 $A, B, and C are capable of completing a job in 30, 45, and 90 days, respectively. A works every day, while B and C join A every fifth day. How long will it take to finish the task?$
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Question 4
16 Sep 2025 S2
61 $A, B, and C can complete a certain task in 20, 30, and 60 days, respectively. How many days will it take for A to finish the work if he receives help from B and C every third day?$
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Question 1