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? February 2, 2024 – by admin 0A. 12B. 16C. 9D. 231 to 9 = 9 * 9 = 811 to 5 = 5 * 10 = 505 to 9 = 5 * 8 = 405th = 50 + 40 = 90 – 81 = 9