Simple interest: find the rate

This type of question, asked 3 times: 14 Sep 2025 S3, 16 Sep 2025 S2, 23 Sep 2025 S1. All 3 questions below, oldest first.

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Question 1
14 Sep 2025 S3
22 $A sum becomes 2.5 times in 10 years under simple interest. Find the rate.$
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Question 2
16 Sep 2025 S2
21 $A principal amount of ₹1,000 yields a simple interest of ₹180 over a period of 2 years. What is the annual rate of simple interest?$
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Question 3
23 Sep 2025 S1
15 $A sum doubles in 5 years at simple interest. What is the annual rate?$
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Question 1