Question: The average of 9 observations was 9, that of the 1st of 5 being 10 and that of the last 5 being 8. What was the 5th observation?\nOptions:\n(A) 9\n(B) 8\n(C) 7\n(D) 6\n(E) 2 Let's think first. Some random reasoning:
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1 to 9 = 9 * 9 = 81\n1 to 5 = 5 * 10 = 50\n5 to 9 = 5 * 8 = 40\n5th = 50 + 40 = 90 – 81 = 9 The final answer: (A).
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