Free articles scheme (buy n get m free, sell 8 at the price of 6) as an effective discount

This type of question, asked 2 times: 3 Feb 2022 Tier II, 20 Jan 2025 Tier II. All 2 questions below, oldest first.

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Question 1
3 Feb 2022 Tier II
60 $A dealer offers a cash discount of 20% and still makes a profit of 20%. If he further sells 8 articles at a rate of 6 articles, then how much percentage above the cost price does he mark on each article?$
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Question 2
20 Jan 2025 Tier II
3 $Murlidhar, the owner of a grocery store, offers a discount scheme 'buy 5 water bottles get 1 for free' to his customers. What is the effective percentage discount offered by Murlidhar? (correct up to two decimal places)$
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Question 1