Average of the first n even or odd numbers

This type of question, asked 3 times: 8 Aug 2022 Tier II, 18 Jan 2025 Tier II, 20 Jan 2025 Tier II. All 3 questions below, oldest first.

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Question 1
8 Aug 2022 Tier II
11 $What is the difference between the average of first 148 even positive numbers and the average of first 129 odd positive numbers?$
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Question 2
18 Jan 2025 Tier II
17 $The average of first 91 even numbers is$
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Question 3
20 Jan 2025 Tier II
9 $The average of first 92 even numbers is$
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