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Whole-set and block averages with the last few numbers related: average of two of them

This type of question, asked 3 times: 12 Sep 2024 S1, 12 Sep 2025 S1, 13 Sep 2025 S2. All 3 questions below, oldest first.

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  1. Question 1

    12 Sep 2024 S1

    61
    The average of 12 numbers is 48. The average of the first 5 numbers is 45 and the average of next 4 numbers is 52. If the 10th10^{\text{th}} number is 10 less than the 11th11^{\text{th}} number and is 5 more than the 12th12^{\text{th}} number, then the average of the 11th11^{\text{th}} and 12th12^{\text{th}} numbers is:

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  2. Question 2

    12 Sep 2025 S1

    58
    The average of 15 numbers is 80. The average of the first 6 numbers is 72. The average of the next 6 numbers is 25%25\% more than the average of the first 6 numbers. The 13th number is 8 more than the 15th number, and the 14th number is 10 less than the 15th number. What is the average of the 13th and 14th numbers?

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  3. Question 3

    13 Sep 2025 S2

    58
    The average of 13 numbers is 70. The average of the first five numbers is 60. The average of the next five numbers is 25%25\% higher than the average of the first five numbers. The 11th number is 6 less than the 13th number, and the 12th number is 4 greater than the 13th number. What is the average of the 11th and 12th numbers?

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