Cost and selling price linked by counts or a linear relation (SP of n = CP of m): profit percent

This type of question, asked 3 times: 29 Jan 2022 Tier II, 3 Feb 2022 Tier II, 18 Jan 2025 Tier II. All 3 questions below, oldest first.

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Question 1
29 Jan 2022 Tier II
13 $If the selling price of 7 articles is equal to the cost price of 8 articles, then what is the profit percentage (correct to one decimal place)?$
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Question 2
3 Feb 2022 Tier II
6 $In a medical transaction, 17 times the cost price is equal to 8 times the sum of the cost price and the selling price. What is the gain or loss percentage?$
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Question 3
18 Jan 2025 Tier II
3 $A man buys 10 identical articles for a total of ₹15. If he sells each of them for ₹1.7, then his profit percentage will be ______%'(rounded off to two decimal place).$
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Question 1